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Effects of a tannic acid blend (ByPro; Silvateam USA, Ontario, CA) added to steam-flaked corn–based fishing diets on beef cattle growth performance, carcass characteristics, nutrient digestibility, fecal N volatilization, and meat lipid oxidation were evaluated. Steers (n= 144; 349 ± 25 kg initial BW) were blocked by initial BW and assigned randomly to 1 of 3 treatments with 12 pens/treatment and 4 steers/pen and fed ad libitum. Treatments included a control (CON; no ByPro) and ByPro fed at 30 or 60 g DM/steer daily (30-ByPro and 60-ByPro, respectively). Pen fecal samples were collected 7 d after cattle were shipped to slaughter for estimation of N volatilization. Strip loins were aged for 21 d for evaluation of color and antioxidant activity. Intake quadratically increased (P= 0.05) from d 0 to 35, whereas linear trends were observed for increased DMI from d 0 to 105 and d 0 to slaughter (P= 0.07 and P= 0.06, respectively), resulting in a 3.7% greater overall DMI for 60-ByPro than for CON. No differences were detected for carcass-adjusted ADG (P= 0.65) or G:F (P= 0.17). Carcass characteristics including HCW (P= 0.52), fat thickness (P= 0.32), LM area (P= 0.57), quality grade (P= 0.44), yield grade (P= 0.29), and percentage of condemned livers (P= 0.13) were not affected by treatments. Apparent total tract digestibility of starch linearly decreased tendency (P= 0.03) with increasing ByPro dose, whereas tends for a linear decrease (P= 0.09) in CP and a quadratic increase (P= 0.09) in OM digestibility were observed. No effects of treatment (P≥ 0.39) were noted for fecal N volatilization. An increase (P< 0.01) in metmyoglobin in strip loin steaks was observed with ByPro inclusion. Oxymyoglobin decreased (P< 0.01) as display day progressed, except on d 5, at which time CON and 30-ByPro steaks had lower proportions than 60-ByPro steaks. Only subtle changes in discoloration ratio and deoxymyoglobin were observed, whereas no effects (P≥ 0.43) for pH or thiobarbituric acid reactive substances were noted. Feeding ByPro increased DMI during the first half of the feeding period without negatively affecting gain efficiency; however, fecal N retention was not altered by ByPro. ByPro did not negatively affect meat quality or carcass characteristics, and it did not seem to affect retail meat antioxidant activity.

This experiment evaluated the dose and payout pattern of trenbolone acetate (TBA) and estradiol-17β (E2) on LM mRNA expression of adenosine monophosphate-activated protein kinase-ɑ (AMPK-ɑ), C/EBPβ, G protein-coupled receptor 41(GPR41), G protein-coupled receptor 43 (GPR43), PPARγ, and stearoyl CoA desaturase (SCD) in finishing feedlot steers as indicators of adipogenesis and marbling development. British · Continental steers (n = 168; 14 pens/treatment; initial BW = 362 kg) were used in a randomized complete block design. Treatments included: no implant (NI), Revalor-S (REV-S; 120 mg TBA + 24 mg E2), or Revalor-XS (REV-X; delayed release implant: 80 mg TBA + 16 mg E2[uncoated], 120 mg TBA + 24 mg E2[coated], 200 mg TBA + 40 mg E2[total]). Steers were fed 1 time daily for an average of 164 d. The LM biopsies were collected (1 steer/pen) on d -1, 27, 55, and 111 relative to timing of implant. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure quantity of AMPK-ɑ, C/EBPβ, GPR41, ,it, PPARγ, and SCDmRNA. No implant · day interactions were detected (P≥ 0.19) in this experiment. Day impacted the mRNA expression of all adipogenic genes (P≤ 0.02). The main effect of implant tended (P= 0.09) to influence expression of AMPK-ɑ, REV-X had an 8.8% increase over NI and an 18.7% increase over REV-S. Implant influenced (P= 0.03) mRNA expression of GPR41, expression of GPR41for the REV-X treatment was not different (P> 0.10) from NI, and both were greater (P≤ 0.05) than REV-S (1.13, 1.00, and 0.67 ± 0.224 arbitrary units) for REV-X, NI, and REV-S, respectively. Implant also influenced (P= 0.02) expression of GPR43, expression of GPR43for REV-X was not different (P> 0.10) from NI, and both were greater (P≤ 0.05) than REV-S (1.27, 1.07, and 0.72 ± 0.234 arbitrary units) for REV-X, NI, and REV-S, respectively. Implant influenced (P= 0.02) mRNA expression of PPARγ in LM tissue, expression of PPARγ for REV-X was not different (P> 0.10) from NI, and both were greater (P≤ 0.05) than REV-S (1.09, 1.02, and 0.69 ± 0.195 arbitrary units) for REV-X, NI, and REV-S, respectively. The REV-X steers received the greatest anabolic dose of TBA + E2without detriment to marbling scores. The increased mRNA expression of adipogenic genes for REV-X steers suggest that the delayed and gradual release of anabolic stimulants associated with REV-X might have mitigated decreases in marbling generally attributed to multiple combined TBA + E2implants.

One hundred ninety-two steers (BW = 354 ± 23.5 kg) were used in a randomized block design to evaluate the effects of ionophore and ractopamine hydrochloride (RH) supplementation strategies on performance and carcass characteristics. Twelve pens of 4 steers were assigned to each of the following treatments: unsupplemented control (CON), laidlomycin propionate (12.1 mg/kg DM) with or without RH (LPRH and LP, respectively), and monensin sodium (36.4 mg/kg DM) with RH (MSRH). Steers were fed for 151 d, of which respective treatments received RH (Actogain; Zoetis, Florham Park, NJ) at a rate of 300 mg/(animal · d) for the final 32 d. Laidlomycin was removed from the LPRH treatment during this period, as no combination feeding has been approved. Upon harvest, carcass data were collected by trained personnel, and subsequent analysis of the LM was conducted to estimate tenderness using Warner-Bratzler shear force (WBSF). Prior to RH supplementation, both LP and LPRH had greater ADG (P≤ 0.02) and G:F (P< 0.01) than CON, whereas MSRH was intermediate. During the final 32 d, MSRH improved G:F (P≤ 0.02) compared to all other treatments and tended to increase ADG over unsupplemented controls (P= 0.05). Cattle receiving LP without RH had significantly greater BW at d 151 than CON (P= 0.02), whereas both RH treatments tended to improve final BW (P≤ 0.09). Ionophores improved ADG (P≤ 0.03) and G:F (P< 0.01) for the entire feeding period, and although LP-supplemented cattle had greater DMI for the final 32 d than both RH treatments (P≤ 0.01), intakes for the 151-d trial were similar among treatments. Carcass weights were greater (P= 0.04) in cattle fed LP with no RH than CON, where cattle yielded an average of 12 kg more HCW. Ractopamine increased LM area in MSRH-supplemented cattle (P= 0.03) and tended to increase LM area for steers receiving LPRH (P= 0.07). Longissimus steaks of MSRH-supplemented cattle had greater WBSF values than CON (P= 0.04) after 7 d of postmortem aging and greater WBSF values than LPRH steaks after 28 d (P= 0.03). All other carcass and WBSF measurements were similar among treatments. The results of this study indicate that LP supplementation without RH may yield a performance similar to and carcass responses associated with the administration of a β-agonist. These results also suggest that performance and carcass characteristics for cattle fed LP are similar to those of cattle fed monensin throughout the feeding period.

Vitamin D3(D3) supplementation may be used to increase tenderness in beef from cattle fed zilpaterol hydrochloride (ZH). The study was arranged as a 2 × 2 factorial with fixed effects of ZH (no ZH or ZH fed at 8.3 mg/kg DM for 20 d with a 3-d withdrawal) and D3 (no D3 or 500,000 IU D3·steer−1·d−1for 10 d prior to harvest). Cattle (n= 466) were harvested in 2 blocks on the basis of BW with subsequent collection of carcass data. Full loins and inside rounds (n= 144 of each subprimal) were collected for fabrication of 5 steaks from the longissimus lumborum (LL), gluteus medius (GM), and semimembranosus (SM), which were aged for 7, 14, 21, 28, or 35 d. Warner-Bratzler shear force (WBSF) was used to evaluate mechanical tenderness of LL, GM, and SM steaks at all aging periods. Slice shear force (SSF) analysis was conducted on only 14- and 21-d LL steaks. No interactions (P> 0.05) between ZH and D3 occurred throughout the entire study. Supplementing ZH resulted in increased HCW (P< 0.01), larger LM area (P< 0.01), and improved calculated yield grades (P< 0.01) with decreases in fat thickness (P= 0.02) and marbling scores (P= 0.05). Supplementation with D3 increased calculated yield grade (P< 0.01) and decreased (P= 0.01) rib eye area. Feeding ZH increased (P≤ 0.05) WBSF of LL steaks at each postmortem age interval, whereas D3 had no effect (P> 0.05) on WBSF or SSF of LL steaks. Like for WBSF, ZH supplementation increased SSF values at 14 and 21 d postmortem (P< 0.01) compared with those for non-ZH steaks. There was an interaction between ZH and postmortem age (P< 0.01) for WBSF of LL steaks. At 7 d LL steaks from ZH steers sheared over 0.6 kg greater than non-ZH steaks; however, by 21 d this difference was reduced to an average of 0.2 kg. Differences in distribution between LL steaks below 3.0 kg from non-ZH and ZH-fed cattle were also notable (P≤ 0.05) through 21 d of aging. At 35 d postmortem a high proportion of LL steaks (68.5%) from ZH-fed steers required less than 3.0 kg to shear. Supplementation with ZH and D3 had no impact (P> 0.05) on WBSF values of GM steaks. Feeding ZH did not alter WBSF of SM steaks, but at 28 d D3 increased (P= 0.04) WBSF values. Shear force in ZH steaks was not effectively reduced by feeding D3 for 10 d to steers prior to harvest. Aging, however, was an effective method of reducing initially greater shear force values in LL steaks and, to a lesser degree, GM steaks from ZH-fed cattle.

We hypothesized that fatty acids would differentially affect G protein coupled receptor (GPR) 43 mRNA expression and GPR43 protein concentrations in bovine intramuscular (IM) and subcutaneous (SC) adipocytes. The GPR43 protein was detected in bovine liver, pancreas, and semimembranosus (MUS) muscle in samples taken at slaughter. Similarly, GPR43 protein levels were similar in IM adipose tissue and SM muscle but was barely detectable in SC adipose tissue. Primary cultures of IM and SC stromal vascular cells were isolated from bovine adipose tissues. Oleic acid (100 μM) stimulated PPARγ gene expression and decreased stearoyl-CoA desaturase (SCD) gene expression but had no effect on GPR43 gene expression, which was readily detectable in both IM and SC adipocytes. Differentiation cocktail (Diff; 10 μMinsulin, 4 μMdexamethasone, and 10 μMciglitizone) stimulated CCAAT/enhancer-binding protein β (C/EBPβ) and PPARγ gene expression in SC but not IM adipocytes, but Diff increased SCD gene expression in both cell types. Linoleic acid (10 µM) increased PPARγ gene expression relative to Diff cocktail in SC adipocytes, whereas linoleic acid and α-linolenic decreased SCD gene expression relative to control adipocytes and adipocytes incubated with Diff (P< 0.05). Increasing concentrations of oleic acid (1, 10, 100, and 500 μM) increased GPR43 protein and mRNA expression in IM but not SC adipocytes. These data indicated that oleic acid alters mRNA and protein concentrations of GPR43 in bovine IM adipocytes.

We present a case study based on balloon‐borne ozone measurements during the SouthEast American Consortium for Intensive Ozonesonde Network Study in August–September 2013. Data from Socorro, NM (34°N, 107°W) show a layer of anomalously low ozone in the upper troposphere (UT) during 8–14 August. Back trajectories, UT jet analyses, and data from the Microwave Limb Sounder (MLS) on the Aura satellite indicate that this feature originated from the marine boundary layer in the eastern/central tropical Pacific, where several disturbances and one hurricane (Henriette) formed within an active region of the Intertropical Convergence Zone in early August 2013. The hurricane and nearby convection pumped boundary layer air with low ozone (20–30 ppbv) into the UT. This outflow was advected to North America 3–5 days later by a strong subtropical jet, forming a tongue of low ozone observed in MLS fields and a corresponding layer of low ozone in Socorro vertical profiles. Impacts of a tropical cyclone are seen in tropospheric ozone at midlatitudes

Feeding zilpaterol hydrochloride (ZH) with ruminally protected AA was evaluated in a small-pen feeding trial. Crossbred steers (n= 180; initial BW = 366 kg) were blocked by weight and then randomly assigned to treatments (45 pens; 9 pens/treatment). Treatment groups consisted of no ZH and no AA (Cont−), ZH and no AA (Cont+), ZH and a ruminally protected lysine supplement (Lys), ZH and a ruminally protected methionine supplement (Met), and ZH and ruminally protected lysine and methionine (Lys+Met). Zilpaterol hydrochloride (8.3 mg/kg DM) was fed for the last 20 d of the finishing period with a 3-d withdrawal period. Lysine and Met were top dressed daily for the 134-d feeding trial to provide 12 or 4 g·hd−1·d−1, respectively, to the small intestine. Carcass characteristics, striploins, and prerigor muscle samples were collected following harvest at a commercial facility. Steaks from each steer were aged for 7, 14, 21, and 28 d, and Warner-Bratzler shear force (WBSF) was determined as an indicator of tenderness. Prerigor muscle samples were used for immunohistological analysis. Cattle treated with Met and Lys+Met had increased final BW (P< 0.3) and ADG (P< 0.05) compared to Cont− and Cont+. Supplementation of Lys, Met, and Lys+Met improved G:F (P< 0.05) compared to Cont− during the ZH feeding period (d 111 to 134) as well as the entire feeding period (P< 0.05). Zilpaterol hydrochloride increased carcass ADG (P< 0.05) when compared to non-ZH-fed steers. Methionine and Lys+Met treatments had heavier HCW (P< 0.02) than that of Cont−. Yield grade was decreased (P< 0.04) for Cont+ steers compared to steers treated with Lys, Lys+Met, and Cont−. Tenderness was reduced (P< 0.05) with ZH regardless of AA supplementation. Lysine, Met, Lys+Met, and Cont+ had less tender steaks (P< 0.05) throughout all aging groups compared to Cont−. Steaks from Lys-treated steers were less tender (P< 0.05) than those of Cont+ during the 7- and 14-d aging periods. Nuclei density was the greatest with Cont− cattle compared to all other treatments suggesting a dilution effect of the nuclei in the larger muscle fibers with ZH feeding. Supplementation of Met in conjunction with ZH feeding increased ADG and HCW although this may lead to decreased tenderness even after aging for 28 d. These findings indicated that steers fed ZH may require additional AA absorbed from the small intestine to maximize performance.

A U.S. consumer (n= 642) study (Baltimore, MD; Phoenix, AZ; and Lubbock, TX) was conducted to compare consumer sensory scores of U.S. beef (83 USDA Choice [Choice] and 96 USDA Select [Select]) and Canadian beef (77 AAA and 82 AA) strip loins. Strip loins (n= 338) were obtained from beef processors in Canada and the United States and were wet aged until 21 d postmortem at 2°C. Marbling scores were assigned at 21 d and loins were paired according to quality grades and marbling score. Strip loins were fabricated into 2.54-cm thick steaks; steaks were vacuum packaged and frozen until further evaluations. Proximate analysis was performed to compare fat, moisture, and protein. Choice and Canadian AAA had similar marbling scores and intramuscular fat. Both Choice and Canadian AAA had greater (P< 0.05) marbling scores and intramuscular fat than Canadian AA, but Select strip loins had intermediate values that were not different from any of the other grades (P> 0.05). Consumers' opinions did not differ when comparing equivalent grades (Choice with Canadian AAA and Select with Canadian AA), but they rated Choice and Canadian AAA more palatable than Select and Canadian AA for all sensory attributes (P< 0.05). Regarding percentage of acceptability and likelihood to buy score, consumers indicated a preference and greater probability to buy (P= 0.001 and P= 0.004, respectively) strip loin steaks from higher quality grade carcasses (Choice and Canadian AAA) than lower quality grade carcasses (Select and Canada AA). Additionally, consumers gave their opinion of Canadian beef, where its quality and safety were rated as “good” to “excellent” for both attributes (76.72% and 88.36%, respectively; P< 0.05), feeling confident in beef that is imported from Canada. In the same way, consumers indicated that country-of-origin labeling was a minimal factor influencing their beef steak purchasing decisions. Results from this consumer study indicated U.S. consumers could not differentiate between U.S. and Canadian beef within comparable quality grades; however, strip loin steaks from higher quality grades were more palatable than lower quality grades according to consumer scores for eating quality traits.

British × Continental steers (n= 168; 7 pens/treatment; initial BW = 362 kg) were used to evaluate the effect of dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E2) and feeding of zilpaterol hydrochloride (ZH) on serum urea-N (SUN), NEFA, IGF-I, and E2concentrations and LM mRNA expression of the estrogen (ER), androgen (ANR), IGF-I (IGF-IR), β1–adrenergic (β1–AR), and β2–adrenergic (β2–AR) receptors and IGF-I. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. Main effects were implant (no implant [NI], Revalor-S [REV-S; 120 mg TBA + 24 mg E2], and Revalor-XS [REV-X; 200 mg TBA + 40 mg E2]) and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal). Steers were fed for 153 or 174 d. Blood was collected (2 steers/pen) at d –1, 2, 6, 13, 27, 55, 83, 111, and 131 relative to implanting; LM biopsies (1 steer/pen) were collected at d –1, 27, 55, and 111. Blood and LM samples were collected at d –1, 11, and 19 relative to ZH feeding. A greater dose of TBA + E2in combination with ZH increased ADG and HCW in an additive manner, suggesting a different mechanism of action for ZH and steroidal implants. Implanting decreased (P< 0.05) SUN from d 2 through 131. Feeding ZH decreased (P< 0.05) SUN. Serum NEFA concentrations were not affected by implants (P= 0.44). There was a day × ZH interaction (P= 0.06) for NEFA; ZH steers had increased (P< 0.01) NEFA concentrations at d 11 of ZH feeding. Serum E2was greater (P< 0.05) for implanted steers by d 27. Serum trenbolone-17β was greater (P< 0.05) for implanted steers by d 2 followed by a typical biphasic release rate, with a secondary peak at d 111 for REV-X (P< 0.05) implanted steers. Implanting did not affect mRNA expression of the ANR or ER, but the IGF-IR and the β1–AR and β2–AR were less (P< 0.05) for REV-S than NI at d 55 and β2–AR mRNA was less (P< 0.05) for REV-S than for REV-X. Expression of the IGF-IR and the β1–AR at d 111 was greater (P< 0.05) for REV-X than for REV-S and NI at d 111, and the β2–AR was less (P< 0.05) for REV-S than for REV-X. Feeding ZH did not affect mRNA expression of the β1–AR and β2–AR. Both implanting and feeding ZH decreased SUN, but a greater dose of TBA + E2did not result in further decreases. In addition, feeding ZH increased serum NEFA concentrations. Metabolic changes resulting from implanting and feeding ZH may aid in explaining steer performance and carcass responses to these growth promotants.

We hypothesized that supplementing finishing diets with palm oil would promote adipocyte differentiation in subcutaneous adipose tissue of feedlot steers, and that soybean oil supplementation would depress adipocyte differentiation. Twenty-eight Angus steers were assigned randomly to 3 groups of 9 or 10 steers and fed a basal diet without additional fat (control), with 3% palm oil (rich in palmitic acid), or with 3% soybean oil (rich in polyunsaturated fatty acids), for 10 wk, top-dressed daily. Palm oil had no effect (P > 0.05) on ADG, food intake, or G:F, whereas soybean oil depressed ADG (P = 0.02), food intake (P = 0.04), and G:F (P = 0.05). Marbling scores tended (P = 0.09) to be greater in palm oil-fed steers (Modest(09)) than in soybean oil-fed steers (Small(55)). Subcutaneous adipocyte mean volume was greater in palm oil-fed steers (515.9 pL) than in soybean-supplemented cattle (395.6 pL; P = 0.01). Similarly, glucose and acetate incorporation into total lipids in vitro was greater in subcutaneous adipose tissue of palm oil-fed steers (119.9 and 242.8 nmol·3h(-1)·10(5) cells, respectively) than adipose tissue of soybean oil-fed steers in (48.9 and 95.8 nmol·3h(-1)·10(5) cells, respectively). Glucose-6-phosphate dehydrogenase and NADP-malate dehydrogenase activities were greater (P ≤ 0.05) in subcutaneous adipose tissue of palm oil-fed steers than in adipose tissue of control steers. Palm oil did not increase palmitic acid or decrease oleic acid in subcutaneous adipose tissue or LM, but decreased (P ≤ 0.05) myristoleic, palmitoleic, and cis-vaccenic acid in adipose tissue, indicating a depression in stearoyl-coenzyme A desaturase activity. Soybean oil increased the proportion of α-linolenic acid in adipose tissue and muscle and increased linoleic acid and 18:1trans-10 in muscle. We conclude that palm oil supplementation promoted lipid synthesis in adipose tissue without depressing feed efficiency or increasing the palmitic acid content of beef.

Crossbred steers (n = 20; 235 ± 4 kg) were fed for 53 d during a receiving period to determine if supplementing chromium (Cr; KemTRACE Chromium Propionate 0.04%, Kemin Industries, Des Moines, IA) would alter glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (Con) or 0.2 mg/kg of Cr to the total diet on a DM basis. Cattle were fitted with jugular catheters on d 52. A glucose tolerance test (GTT) and an insulin sensitivity test (IST) were conducted on d 53. Blood samples were collected from –60 to 150 min relative to each infusion. Serum was isolated to determine glucose, insulin, and NEFA concentrations. Throughout GTT, no differences were detected in glucose concentrations, glucose clearance rates (k), or preinfusion insulin concentrations (P> 0.50), but insulin concentrations postinfusion tended (P= 0.06) to be greater for the Cr-supplemented steers. This caused an increase in the insulin to glucose ratio (I:G) from 0 to 150 min postinfusion for the Cr-supplemented steers (P= 0.03). In addition, NEFA concentrations during GTT were lower (P≤ 0.01) for Cr-supplemented steers both preinfusion and postinfusion. During IST, there was no treatment effect on glucose concentrations preinfusion (P= 0.38), but postinfusion glucose concentrations were greater (P< 0.01) in the Cr-supplemented steers. The kof Cr-supplemented steers tended (P= 0.06) to be faster than Con steers from 30 to 45 min postinfusion. During the same test, there was no treatment effect detected for insulin concentrations (P> 0.33). The I:G were not affected by treatment (P> 0.40).Concentrations of NEFA were reduced (P< 0.01) both preinfusion and postinfusion during IST for Cr-supplemented steers. Results of this study indicate that supplementation of Cr can significantly alter lipid metabolism. This suggests that these steers had less dependence on lipid metabolism for energy or sensitivity of adipose tissue to antilipolytic signals was reduced. Results of glucose and insulin metabolism were inconsistently modified after a GTT and an IST.

Crossbred steers (n = 180; 230 ± 6 kg) were fed during a 56-d receiving period to determine if supplementing chromium (Cr; KemTRACE Chromium Propionate 0.04%, Kemin Industries) would improve feedlot performance and health of newly-received cattle. A completely randomized block design (36 pens; 9 pens/treatment; 5 steers/pen) was used. Chromium premixes were supplemented to add 0 (Con), 0.1, 0.2, or 0.3 mg/kg of Cr to the total diet on a DM basis. No differences were detected on d 0 or after the first 14 d on feed. From d 0 to d 28, DMI (P= 0.07) and ADG increased linearly (P= 0.04) as Cr concentrations increased. From d 0 to d 56, BW (P =0.08) displayed a tendency to increase linearly, and consequently ADG and G:F increased linearly (P≤ 0.05) as Cr concentrations increased. The number of steers treated at least once for respiratory symptoms tended (P= 0.07) to linearly decrease as Cr concentrations increased. Twenty additional steers (235 ± 4 kg) were fed 56 d to determine if supplementing Cr (Con or 0.2 mg/kg Cr) would alter the metabolic response of newly-received cattle to a lipopolysaccharide (LPS) challenge. Cattle were fitted with jugular catheters on d 52. On d 55, blood samples were collected at 0.5-h intervals from −2 to 8 h, and again at 24 h relative to a LPS challenge (0.5 μg/kg BW) at 0 h. Serum glucose, insulin, and NEFA concentrations were determined from blood samples. Steer BW was also measured at cannulation, and 24 h and 8 d post-LPS. Steer BW did not differ at cannulation (P= 0.37), but 24 h post-LPS, Cr-supplemented steers had lost less BW (P= 0.03). Pre-LPS glucose concentration did not differ (P= 0.97). Post-LPS, there was a time × treatment interaction (P< 0.01) such that glucose concentration peaked earlier (0.5 h) and at a greater concentrations in Cr-supplemented steers (P< 0.01). Insulin concentration did not differ between treatments pre- or post-LPS (P> 0.13). Concentration of NEFA did not differ pre-LPS (P= 0.54); but 0.5 h post-LPS Cr-treated steers produced a greater peak NEFA concentration (P< 0.04). Results of this study indicate that supplementation of Cr to the basal diet can have beneficial effects on the performance and health of newly-received steers. These data also suggest that supplementation of Cr attenuated BW loss and allowed for a quicker recovery after a LPS challenge.

An experiment was conducted to determine the effects of zilpaterol hydrochloride mMsupplementation (ZH; 8.3 mg/kg on a DM basis for 20 d) and calcium chloride injection [CaCl2, 200 at 5% (wt/wt) at 72 h postmortem] on palatability traits of beef (Bos taurus) strip loin steaks. Select (USDA) strip loins were obtained from control (no ZH = 19) and ZH-supplemented carcasses (n = 20). Right and left sides were selected alternatively to serve as a control (no INJ) or CaCl2–injected (INJ) and stored at 4°C. Before injecting the subprimals (72 h postmortem), 2 steaks were cut for proximate, sarcomere length, and myofibrillar fragmentation index (MFI) analyses. At 7 d postmortem each strip loin was portioned into steaks, vacuum packaged, and aged for the appropriate period for Warner-Bratzler shear force (WBSF; 7, 14, 21, and 28 d postmortem), trained sensory analysis (14 and 21 d postmortem), purge loss (7 d), and MFI (3, 7, 14, 21, and 28 d postmortem). Results indicated steaks from both ZH supplementation and INJ had reduced WBSF values as days of postmortem aging increased. The WBSF values of ZH steaks were greater (P< 0.05) than no ZH steaks at each postmortem aging period. The INJ steaks had lower WBSF values (P< 0.05) than non-injected steaks. A greater percentage (91 vs. 71%) of steaks had WBSF values < 4.6 kg from steers with no ZH supplementation at 7 d postmortem, but the percentage did not differ (P> 0.05) due to ZH at 14, 21, or 28 d or due to INJ at any aging period. Trained panelists rated tenderness less in ZH steaks than steaks with no ZH at 14 d and 21 d. However, INJ improved (P< 0.05) the tenderness ratings and flavor intensity of the trained panelists, compared with their non-injected cohorts at 21 d. Zilpaterol hydrochloride supplementation reduced (P< 0.05) MFI values, but INJ resulted in greater (P< 0.05) MFI values compared with no INJ. Subprimals from ZH and INJ showed greater purge loss (P< 0.05). Although no interactions were found with ZH and CaCl2, injecting USDA Select strip loins from ZH-fed cattle can help reduce the normal WBSF variation as it does in steaks from non-ZH-fed cattle.

British × Continental heifers (n = 3,382; initial BW = 307 kg) were serially slaughtered to determine if increasing days on the finishing diet (DOF) mitigates negative consequences of zilpaterol HCl (ZH) on quality grade and tenderness of beef. A 2 × 3 factorial arrangement of treatments in a completely randomized block design (36 pens; 6 pens/treatment) was used. Zilpaterol HCl (8.33 mg/kg DM) was fed 0 and 20 to 22 d before slaughter plus a 3 to 5 d withdrawal to heifers spending 127, 148, and 167 DOF. Feedlot and carcass performance data were analyzed with pen as the experimental unit. Three hundred sixty carcasses (60 carcasses/treatment) were randomly subsampled, and strip loin steaks were aged for 7, 14, and 21 d for assessment of Warner-Bratzler shear force (WBSF) and slice shear force (SSF) with carcass serving as the experimental unit for analysis. No relevant ZH × DOF interactions were detected (P > 0.05). Feeding ZH during the treatment period increased ADG by 9.5%, G:F by 12.5%, carcass ADG by 33.6%, carcass G:F by 35.9%, carcass ADG:live ADG by 15.6%, HCW by 3.2% (345 vs. 356 kg), dressing percent by 1.5%, and LM area by 6.5% and decreased 12th-rib fat by 5.2% and yield grade (YG) by 0.27 units (P < 0.01). Feeding ZH tended to decrease marbling score (437 vs. 442 units; P = 0.10) and increased WBSF at 7 (4.25 vs. 3.47 kg; P < 0.01), 14 (3.57 vs. 3.05 kg; P < 0.01), and 21 d (3.50 vs. 3.03 kg; P < 0.01). Feeding ZH decreased empty body fat percentage (EBF; 29.7% vs. 30.3%; P < 0.01) and increased 28% EBF adjusted final BW (473.4 vs. 449.8 kg; P < 0.01). Analysis of interactive means indicated that the ZH × 148 DOF group had a similar percentage of USDA Prime, Premium Choice, Low Choice, and YG 1, 2, 3, 4, and 5 carcasses (P > 0.10) and decreased percentage of Select (30.4 vs. 36.6%; P = 0.03) and Standard (0.2 vs. 0.9%; P = 0.05) carcasses compared with the control × 127 DOF group. As a result of ZH shifting body composition, extending the DOF of beef heifers is an effective feeding strategy to equalize carcass grade distributions. This can be accomplished along with sustaining the ZH mediated advantages in feedlot and carcass weight gain.

We have demonstrated that among carcass adipose tissue depots, brisket subcutaneous adipose tissue contains the greatest concentration of MUFA and lowest concentration of SFA. Therefore, we hypothesized that brisket subcutaneous adipose tissue depots would exhibit greater adipogenic gene expression over time than other major subcutaneous adipose tissue depots. Four Angus steers, each at 9, 12, 14, and 16 mo of age, were harvested and fresh subcutaneous adipose tissue samples were collected from over the brisket, chuck, rib, loin, sirloin, round, flank, and plate. Relative gene expression for C/EBPβ, PPARγ, carnitine palmitoyltransferase-1 beta (CPT-1β), stearoyl-coenzyme A desaturase (SCD), AMP-activated protein kinase alpha (AMPKα), and G-coupled protein receptor 43 (GPR43) was analyzed by quantitative real-time PCR. Expression of C/EBPβ, PPARγ, and CPT-1β was greatest at 12 to 14 mo of age (all P < 0.0001) and declined to very low abundance by 16 mo of age in all depots. Expression of PPARγ and CPT-1β was greater (P < 0.03) in flank, rib, and sirloin subcutaneous adipose tissues than in brisket and round adipose tissues. The expression of the SCD gene did not differ among the 4 age groups (P = 0.95). The palmitoleic:stearic acid ratio (an estimate of SCD activity) was greater (P < 0.001) in the subcutaneous adipose tissues from brisket, plate, and round than in the loin, rib, and sirloin. Conversely, subcutaneous adipose tissue from the loin, rib, and sirloin had greater (P < 0.001) SCD gene expression than the brisket, plate, and round. In general, subcutaneous adipose tissues with the highest concentration of MUFA and least SFA consistently exhibited the least SCD gene expression and adipogenic gene expression. We conclude that MUFA in the brisket and other depots with large SCD indices were deposited before 9 mo of age, during a time when the subcutaneous adipocytes were highly differentiated.

The objectives of this study were to determine the effects of supplementation with a single β-adrenergic agonist (β-AA) or a sequence of β-AA on cow performance, carcass characteristics, and mRNA relative abundance of cull cows implanted and fed a concentrate diet. Sixty cull cows were implanted with Revalor-200 (200 mg of trenbolone acetate and 20 mg of estradiol) and assigned to 1 of 4 treatments (n = 15/treatment): CON = fed a concentrate diet only; RH = supplemented with ractopamine-HCl for the last 25 d before slaughter; ZH = supplemented with zilpaterol-HCl for 20 d before a 3-d withdrawal before slaughter; RH + ZH = supplemented with RH for 25 d, followed by ZH for 20 d before a 3-d withdrawal before slaughter. Ractopamine-HCl was supplemented at a dose of 200 mg·animal(-1)·d(-1), and ZH was supplemented at 8.33 mg/kg (100% DM basis) of feed. All cows were fed a concentrate diet for 74 d. Each treatment had 5 cows per pen and 3 replicate pens. Body weights were collected on d 1, 24, 51, and 72. Muscle biopsies from the LM were collected on d 24, 51, and at slaughter from a subsample of 3 cows per pen. Carcass traits were evaluated postslaughter. The 2 ZH treatments averaged 15.3 kg more BW gain, 0.20 kg greater ADG, and 7.8 cm(2) larger LM area than CON and RH treatments, and 21 kg more HCW than CON, but these differences were not significant (P > 0.10), likely due to a sample size of n = 15/treatment. The sequence of RH followed by ZH tended to optimize the combination of HCW, LM area, percent intramuscular fat, and lean color and maturity compared with the ZH treatment. Abundance of β(2)-adrenergic receptor (AR) mRNA was not altered in the RH + ZH treatment during RH supplementation from d 24 to 51 of feeding. However, the abundance of β(2)-AR mRNA increased (P < 0.05) the last 23 d of feeding for the RH treatment and tended (P = 0.10) to increase in ZH cows during ZH supplementation. For all cows, abundance of type IIa myosin heavy chain (MHC-IIa) mRNA decreased (P < 0.05) after 24 d of feeding. Abundance of MHC-IIx mRNA increased (P < 0.05) for ZH and RH + ZH treatments the last 23 d of feeding during ZH supplementation. Although few significant differences were observed in performance or carcass traits, mRNA quantification indicated that β-AA supplementation elicited a cellular response in cull cows. Implanting and feeding cull cows for 74 d, regardless of β-AA supplementation, added economic value by transitioning cows from a cull cow to what is referred to in industry as a white cow market in which cows have white fat resulting from grain feeding.

Twenty crossbred yearling steers (421 kg) were used to evaluate the effects of implanting with trenbolone acetate (TBA; 120 mg), estradiol-17β (E(2); 25.7 mg), and a combination (120 mg of TBA and 24 mg of E(2)) on adipogenic and myogenic mRNA concentrations. Animals were blocked by BW and within each block were assigned to 1 of 4 treatments. Animals were housed and fed in individual pens with 5 animals per treatment. All animals were weighed weekly, and muscle biopsy samples were taken from the LM of each steer on d 0 (before implantation), 7, 14, and 28. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure the quantity of C/EBPβ, PPARγ, stearoyl CoA desaturase (SCD), myogenin, and 3 isoforms of bovine myosin heavy chain (MHC) mRNA. Total BW gain from the 28-d period was adjusted to d 0 by use of covariant analysis, and steers in the implant groups tended (P = 0.09) to have increased BW gain compared with nonimplanted control steers. Analysis of the gene expression of MHC showed that neither implant nor day (P > 0.20) had a significant effect on the expression of type I or IIX MHC mRNA There was also no treatment effect (P > 0.20) on MHC-IIA and myogenin, but increasing days on feed increased (P = 0.05) the expression of MHC-IIA mRNA. Relative mRNA abundance of C/EBPβ, PPARγ, and SCD increased (P < 0.05) during days of feed but PPARγ decreased (P < 0.05) with the treatment of combined TBA/E(2) implant. Results of this study indicate that implanting with TBA, E(2), or both increased BW gain and decreased adipogenic gene expression of finishing steers without significantly affecting the concentration of type I, IIA, or IIX MHC mRNA. Increasing days on feed increased both MHC-IIA and adipogenic gene expression in bovine skeletal muscle biopsy samples. We conclude that administration of steroidal implants had no effect on the proportion of the 3 MHC mRNA isoforms but decreased C/EBPβ, PPARγ, and SCD mRNA in bovine skeletal muscle.

We predicted that zilpaterol hydrochloride (ZH), a β-adrenergic receptor (AR) agonist, would depress mRNA and protein abundance of β-AR in bovine satellite cells. We also predicted that ZH would decrease total lipid synthesis in bovine adipose tissue. Bovine satellite cells isolated from the semimembranosus muscle were plated on tissue culture plates coated with reduced growth factor matrigel or collagen. Real-time quantitative PCR was used to measure specific gene expression after 48 h of ZH exposure in proliferating satellite cells and fused myoblasts. There was no effect of ZH dose on [(3)H]thymidine incorporation into DNA in proliferating myoblasts. Zilpaterol hydrochloride at 1 µM decreased (P < 0.05) β1-AR mRNA, and 0.01 and 1 µM ZH decreased (P < 0.05) β2-AR and β3-AR mRNA in myoblasts. The expression of IGF-I mRNA tended to increase (P = 0.07) with 1 µM ZH. There was no effect (P > 0.10) of ZH on the β-AR or IGF-I gene expression in fused myotube cultures at 192 h or on fusion percentage. The β2-AR antagonist ICI-118, 551 at 0.1 µM attenuated (P < 0.05) the effect of 0.1 µM ZH to reduce expression of β1- and β2-AR mRNA. The combination of 0.01 µM ZH and 0.1 µM ICI-118, 551 caused an increase (P < 0.05) in β1-AR gene expression. There was no effect (P > 0.10) of ICI-118, 551 or ZH on β3-AR or IGF-I. Western blot analysis revealed that the protein content of β2-AR in ZH-treated myotube cultures decreased (P < 0.05) relative to control. Total lipid synthesis from acetate was increased by ZH in bovine subcutaneous adipose tissue explants in the absence of theophylline but was decreased by ZH when theophylline was included in the incubation medium. These data indicate that ZH alters mRNA and protein concentrations of β-AR in satellite cell cultures, which in turn could affect responsiveness of cells to prolonged ZH exposure in vivo. Similar to other β-adrenergic agonists, ZH had only modest effects on lipid metabolism in adipose tissue explants.

A consumer study was conducted in Lubbock, Texas, to determine the effects of fat level of beef strip steaks on the palatability traits of tenderness, juiciness, flavor liking, and overall liking, while further investigating the window of acceptability for fat content of beef. Thirty beef strip loins were selected by trained personnel to equally represent USDA Prime, High Choice (upper 1/3 Choice), Low Choice (lower 1/3 Choice), Select, and Standard. Proximate analysis was conducted on all strip loins to determine percentage fat, moisture, protein, and collagen. Three strip loins from each quality grade were selected based on fat percentages from proximate analysis to best represent each USDA quality grade for use in the consumer evaluations. Strip loins were fabricated into 2.5-cm steaks, and further processed into 5 × 5 cm pieces. In addition to the US-sourced product, beef LM pieces from 6 Australian Wagyu steers (Wagyu) and 6 Australian grain finished steers (Australian) were used in the consumer evaluations. Consumers (n = 120) were served 7 samples: a warm-up sample, 1 sample from each USDA quality grade treatment, and either a Wagyu or Australian sample, in a balanced order in accordance with a 6 × 6 Latin square. Consumers rated each steak sample for tenderness, juiciness, flavor, and overall liking and rated each palatability trait as either acceptable or unacceptable. Moreover, consumers rated each sample as unsatisfactory, good everyday quality, better than everyday quality, or premium quality. Tenderness, juiciness, flavor liking, and overall liking increased with increasing fat content (P< 0.05). However, Wagyu and Australian samples did not follow this trend for flavor and overall liking. A decrease in consumer acceptability of each palatability trait was observed as fat level decreased (P< 0.05). Consumer overall liking was correlated (P< 0.05) with consumer tenderness (r = 0.76) and juiciness ratings (r = 0.73), but most highly correlated with flavor liking (r = 0.88). Results of this study indicated that increased fat level in beef strip steaks positively affected tenderness, juiciness, flavor liking, and overall liking of beef strip steaks. Moreover, flavor liking was the most highly correlated palatability trait with overall liking. In US-sourced samples, fat level had a large effect on the flavor liking of beef as determined by consumers.

Our objectives were to determine the effects of zilpaterol hydrochloride (ZH) and the release rate of trenbolone acetate and estradiol-17β on the Warner-Bratzler shear force (WBSF) and slice shear force (SSF) of longissimus lumborum (LL) and the WBSF of gluteus medius (GM) and psoas major (PM) in response to various aging periods. British × Continental steers (n = 168) were assigned to treatments in a 3 × 2 factorial. The main effects of treatment were implant (no implant, Revalor-S, Revalor-XS, Intervet/Schering Plough Animal Health, De Soto, KS) and ZH (0 or 8.3 mg/kg of DM for 20 d). Slaughter group was included as a random effect to account for the variation in days on feed (153 or 174 d). Loins (n = 96) were fabricated to obtain strip loin, top sirloin butt, and tenderloin subprimals. Five 2.54-cm steaks were cut from each subprimal and assigned to 1 of 5 aging periods (7, 14, 21, 28, or 35 d postmortem). Feeding ZH increased (P≤ 0.01) LL WBSF and SSF values at each aging period compared with controls. Implanting increased (P< 0.05) LL WBSF values at 14 and 21 d, but did not affect LL SSF values (P> 0.05). Only Revalor-S increased (P≤ 0.05) WBSF values at 28 and 35 d compared with no implant or Revalor-XS. The percentage of LL steaks with a WBSF value below 4.6 kg did not differ (P> 0.05) between ZH supplementation or implant strategy at any aging period, and by d 28, more than 99% of LL steaks registered WBSF values below 4.6 kg. Feeding ZH increased (P< 0.05) GM WBSF values only on d 21. Implant had no effect (P> 0.05) on GM WBSF values. The percentage of GM steaks with a WBSF value below 4.6 kg did not differ (P> 0.05) between ZH supplementation or implant strategy at any aging period. Neither ZH nor implant strategy affected PM WBSF values (P> 0.05). All PM WBSF values were below 4.6 kg on d 7. The results of this study indicated that feeding ZH increased WBSF and SSF of LL steaks, regardless of the aging period; however, the percentage of steaks with WBSF below 4.6 kg did not differ because of ZH or implant. Implanting increased LL WBSF values, but not SSF values. These results showed that although differences existed between implanting, as well as ZH supplementation of British × Continental steers, 99% of LL steaks were classified as tender based on WBSF values by extending aging to 28 d postmortem. It should be noted that 21.2% of 7-d, 13.8% of 14-d, and 17.3% of 21-d ZH steaks had WBSF values greater than 4.6 kg, but 0% of nonsupplemented steaks were greater than 4.6 kg at these aging periods. However, because ZH and implants can increase retail yield of valuable subprimals, such as the tenderloin, considerable value could be captured through ZH supplementation with anabolic implants because shear force was not affected in PM steaks.

Four experiments evaluated the effect of implant dose and release pattern on performance and carcass traits of crossbred beef steers. In Exp. 1, steers (4 to 7 pens/treatment; initial BW = 315 kg) were fed an average of 174 d. Treatments were 1) no implant (NI); 2) Revalor-S [120 mg of trenbolone acetate (TBA) and 24 mg of estradiol 17β (E2); REV-S]; 3) Revalor-IS followed by REV-S (cumulatively 200 mg of TBA and 40 mg of E2; reimplanted at 68 to 74 d; REV-IS/S); and 4) Revalor-XS (200 mg of TBA and 40 mg of E2; REV-X). Carcass-adjusted final BW was greater (P< 0.05) for REV-X and REV-IS/S than for REV-S (610, 609, and 598 kg, respectively). Daily DMI did not differ (P> 0.10) among the 3 implants, but carcass-adjusted G:F was greater (P< 0.05) for REV-X and REV-IS/S than for REV-S (0.197 and 0.195 vs. 0.188). Both HCW and LM area were greater (P< 0.05) for REV-X and REV-IS/S than for REV-S. Marbling scores were greatest (P< 0.05) for REV-S and least (P< 0.05) for REV-IS/S; REV-X was intermediate to NI and REV-IS/S. In Exp. 2, steers (10 pens/treatment; initial BW = 391 kg) were fed 131 d, with treatments of REV-S, REV-IS/S (reimplanted at 44 to 47 d), and REV-X. Carcass-adjusted final BW (598 kg), ADG (1.6 kg), DMI (9.4 kg), G:F (0.17), and HCW did not differ (P> 0.10) among treatments. The percentage of Choice was less (P< 0.05) and percentage of Select greater (P< 0.05) for REV-IS/S than for REV-S and REV-X. In Exp. 3, steers (10 pens/treatment; initial BW = 277 kg) were fed 197 d and received either REV-IS/S (reimplanted at 90 to 103 d) or REV-X. Carcass-adjusted final BW (625 vs. 633 kg) and ADG (1.81 vs. 1.76 kg) were greater (P< 0.05) for REV-X-implanted steers. Daily DMI did not differ, but G:F tended (P< 0.10) to be increased and HCW was greater (P< 0.05) for REV-X than for REV-IS/S. In Exp. 4, steers (8 pens/treatment; initial BW = 238 kg) were fed 243 d and received either REV-IS/S (reimplanted at 68 to 71 d) or REV-X. Carcass-adjusted final BW (612 kg), ADG (1.54 kg), DMI (7.55), and G:F (0.21) did not differ (P> 0.10) for REV-IS/S and REV-X-implanted steers. Carcass traits did not differ among implants, but the percentage of Choice carcasses was greater (P< 0.05) and percentage of Select was less (P< 0.05) for REV-X than for REV-IS/S. These data indicate that when TBA/E2dose is equal, the altered release rate of REV-X can improve performance and quality grade, but these effects depend on duration of the feeding period and timing of initial and terminal implants.

The objective of this study was to determine the effect of feeding zilpaterol hydrochloride (ZH) on the shelf life and stability of ground beef. Beef knuckles and plates were obtained from USDA Select beef heifer carcasses from control (CON) animals or those supplemented with ZH (8.33 mg/kg of dietary DM basis) for the last 20 d of the finishing period. Subprimals were coarsely ground and blended to produce an 80% lean product. The mixture was vacuum-stuffed into chubs and placed in dark storage at 2 to 4°C for 7, 14, or 21 d before fine grinding. Each week, the finely ground samples were packaged on expanded polystyrene trays overwrapped with polyvinyl chloride film and placed in refrigerated retail cases (0 to 2°C) under continuous fluorescent lighting to simulate retail display. Samples were subjected to a variety of analyses at different time intervals (h) during simulated display, including composition analysis, thiobarbituric acid-reacting substance analysis (TBA), sensory color, instrumental color, and aerobic plate count. Data analysis revealed trained sensory color and discoloration scores were similar between CON and ZH-treated samples. Instrumental L* and b* values for CON and ZH-treated samples did not differ (P= 0.13 and 0.19, respectively). Instrumental a* values declined (P< 0.05) over the display period for CON and ZH ground beef. However, a* values for ZH ground beef stored for 7 d were greater (P< 0.05) than CON values at 18 through 72 h of display. There was a treatment × storage day interaction (P< 0.001) for TBA values with ZH having smaller TBA values than CON after 7 d of dark storage. There was no difference (P= 0.21) in aerobic plate count between ZH and CON ground beef samples. Overall, ground beef from cattle supplemented with ZH was equal to or better than CON for sensory color and discoloration, instrumental color, and stability variables, including TBA reactive substances and aerobic plate counts.

Anabolic steroid implants are commonly used to increase growth performance and carcass leanness. The objective of this study was to determine the effects of various trenbolone acetate implants on Warner-Bratzler shear force (WBSF), slice shear force, and consumer palatability ratings for USDA Choice and Select beef strip steaks aged for 14 and 21 d from cattle implanted before slaughter. Beef steers (n = 1,740) were subjected to the following treatments: 1) nonimplanted control (CON); 2) Revalor-IS on d 0 and Revalor-S on d 70 (IS/S); or 3) Revalor-XS (RXS) on d 0, and were randomly assigned to pens within blocks. A subsample of USDA Choice (n = 82) and USDA Select (n = 81) carcasses was selected. Strip loins from these carcasses were collected, and steaks measuring 2.54 cm were fabricated and aged for 14 or 21 d postmortem. Select steaks aged 14 d from RXS cattle had decreased (P< 0.05) WBSF values compared with IS/S steaks, but CON steaks did not differ from either implant treatment. Warner-Bratzler shear force did not differ among treatments (P> 0.05) from USDA Choice steaks aged 14 and 21 d or from Select steaks aged 21 d. Consumer scores for flavor and overall liking for USDA Choice 14-d aged RXS steaks were less (P< 0.05) than CON steaks; however, there were no differences between RXS, IS/S, and CON for tenderness or juiciness, or for tenderness and overall acceptability. Select steaks aged 14 d from IS/S cattle had less (P< 0.05) tenderness, tenderness acceptability, overall acceptability, overall liking, juiciness, and flavor scores than RXS and CON steaks; however, consumers also rated RXS steaks less for tenderness, juiciness, and tenderness acceptability when compared with CON steaks. Consumer scores for overall liking, flavor, and tenderness for USDA Choice steaks aged 21 d from RXS, IS/S, and CON did not differ. However, implant affected (P< 0.05) overall liking, flavor, juiciness, and tenderness for USDA Select steaks aged 21 d. Even so, there were no differences between RXS, IS/S, and CON steaks for tenderness or overall acceptability for steaks aged 21 d, regardless of quality grade. Results indicated that tenderness differences exist among implant strategies when strip steaks were aged 14 d; however, tenderness and overall consumer acceptability were only influenced by implant in Select steaks aged 14 d. Furthermore, aging for 21 d can minimize and even eliminate implant differences in WBSF and slice shear force, as well as tenderness and overall consumer acceptability.

Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E2) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of finishing beef steers. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. British × Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). The main effects of treatment were implant [no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E2); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E2)] and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 or 174 d. No implant × ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg), and G:F (0.14, 0.16, and 0.17) increased (P< 0.05) as TBA and E2dose increased. Implanting increased (P< 0.05) DMI, but DMI did not differ (P> 0.10) between REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P< 0.05) ADG and G:F, but REV-S and REV-X did not differ (P> 0.10). From d 112 to end, ADG increased by 19% (P< 0.05) and G:F was 18% greater (P< 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P< 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P< 0.05) by ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg for REV-S and REV-X, respectively; P< 0.05). An implant × ZH interaction (P= 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P> 0.10) between REV-X and REV-S. With ZH, REV-X increased (1.7%; P< 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P> 0.10) by implant or ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA + E2and extended payout improved steer performance and HCW.

Zilpaterol hydrochloride (ZH) is a β-adrenergic agonist approved to be fed at a rate of 8.3 mg/kg (100% DM basis) during the final 20 to 40 d of the finishing period in beef cattle followed by a minimum 3-d withdrawal period antemortem. The Federal Drug Administration (FDA) approved label claims of increased rate of BW gain, improved feed efficiency, and increased carcass leanness. Before the release of ZH for commercial use in 2007, approximately 10 independent research trials at various universities and commercial feedlots were initiated. Articles in recent issues of the Journal of Animal Scienceare a result of the large comprehensive body of research designed to increase the understanding of the effect of ZH on beef cattle growth, carcass traits, and beef quality. The feeding of ZH for 20 to 40 d with a 3-d withdrawal resulted in significantly increased ADG. The increases equate to an average of 9 kg heavier BW in ZH-fed steers. Hot carcass weight has been shown to increase to a larger degree compared with BW, with an average improvement of 15 kg. Dressing percent is increased by 1.5 to 2.0% with the feeding of ZH. Increases in carcass leanness were reported for cattle fed ZH mainly through a reduction in yield grades. The LM area was increased, along with yield of subprimal cuts from the round, flank, and loin. Warner-Bratzler shear force studies have shown LM steaks from ZH-treated cattle to have increased shear force values of 1.1 to 1.7 kg for 7-d-aged steaks, 0.4 to 1.3 kg for 14-d-aged steaks, and 0.27 to 1.4 kg for 21-d-aged steaks compared with controls. Recent research has suggested that the aging response is normal in ZH steaks. Consumers were able to identify tenderness differences in 14-d-aged Choice steaks from cattle fed ZH for 20 d compared with 14-d-aged steaks from control cattle; this difference was mitigated with 21 d of postmortem aging. Zilpaterol hydrochloride has been shown to increase cattle growth and efficiency as well as lean tissue deposition in the carcass, with some impact on carcass traits such as Warner-Bratzler shear force.

Two trials investigated zilpaterol hydrochloride (ZH) feeding duration, enhancement, blade tenderization, and postmortem aging effect on Warner-Bratzler shear force (WBSF; trial 1) and consumer sensory ratings (trial 2). For trial 1, USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH (6.8 g/t on 90% DM) the last 0, 20, 30, or 40 d of the feeding period. One-half of each strip loin was enhanced (110%) with a brine solution, whereas the remaining portion was not enhanced. Both pieces were portioned into steaks, which were aged 7, 14, or 21 d for WBSF analysis. For trial 2, paired USDA Select beef strip loins were obtained from carcasses of beef steers fed ZH the last 0 or 20 d of feeding. Paired strip loins were fabricated into 4 pieces and assigned to control, moisture enhanced, blade tenderized, and blade tenderized + moisture enhanced treatments. Strip loin pieces were then portioned into steaks that were aged 14 or 21 d postmortem. Consumers panelists (n = 458) indicated their like or dislike of tenderness, juiciness, flavor, and overall like of each sample using 8-point, verbally anchored scales, as well as tenderness and overall acceptability. With exception of 20 d ZH-treated steaks, results from trial 1 indicate WBSF values decreased (P< 0.05) with enhancement. Among enhanced steaks, steaks from cattle fed ZH for 20, 30, and 40 d had greater (P< 0.05) WBSF values than controls. Among nonenhanced steaks, 20 d ZH-treated steaks had WBSF values similar to 0, 30, and 40 d ZH-treated steaks, whereas 30 and 40 d ZH-treated steaks had greater (P< 0.05) WBSF values than controls. Postmortem aging for 21 d improved (P< 0.05) WBSF values for all ZH durations when compared with 7-d aging treatments. Results from trial 2 indicate ZH feeding for 20 d had no effect on flavor scores, decreased tenderness scores (P< 0.05), and tended (P< 0.10) to decrease juiciness and overall like scores when compared with controls for steaks aged 14 d. After 21 d aging, steaks from 20 d ZH-fed cattle had reduced (P< 0.05) tenderness, juiciness, and overall like scores and tended (P< 0.10) to have decreased flavor scores when compared with controls. These results indicate enhancement improved WBSF, but was not sufficient to overcome the detrimental effect of ZH feeding duration on WBSF until steaks were aged for 21 d postmortem. Consumer scores indicate 20 d ZH feeding had no effect on overall acceptability, but decreased tenderness and tenderness acceptability scores when compared with controls.

Enteric disease and immune challenge are processes that have detrimental effects on the growth performance of young swine. The current study tested the hypothesis that salmonella-induced enteric disease would perturb the endocrine growth axis in a serovar-dependent fashion. Specifically, we evaluated the effects of Salmonella entericaserovar Typhimurium (Typhimurium) and serovar Choleraesuis (Choleraesuis) on critical regulatory components of growth in young swine. Weaned pigs were housed 2 per pen with ad libitum access to feed and water in a 14-d experiment. Pigs were then repeatedly fed 108cfu of either Choleraesuis or Typhimurium in dough balls, with control pigs receiving dough without bacteria. Bacteria were refed twice weekly. Rectal temperatures were monitored daily from d 0 to 7 and ADFI was measured through d 14. Pigs were weighed and samples of serum were obtained for circulating IGF-I on d 0, 7, and 14. At the conclusion of the study, samples of semitendinosus muscle and liver were obtained and subsequently assayed for IGF-I, IGFBP-3, and IGFBP-5 mRNA. Rectal temperatures were elevated in pigs given Choleraesuis from d 2 through 7 (P< 0.05) when compared with control pigs and pigs fed Typhimurium. Pigs receiving Choleraesuis had a substantially decreased feed intake on d 2, 3, 4, 7, 8, 9, and 10 (P< 0.01), with a trend for a reduction on d 5 (P= 0.08), and they experienced an approximately 25% reduction in BW compared with control pigs and pigs given Typhimurium by the conclusion of the study. Pigs given Choleraesuis also experienced marked reductions in circulating IGF-I on d 7 (P< 0.01 vs. control and Typhimurium), with reductions of lesser magnitude on d 14 (P= 0.07 vs. control and P< 0.05 vs. Typhimurium). Inoculation tended to affect liver IGFBP-3 mRNA (P= 0.08), for which expression tended to be elevated in pigs given Typhimurium and Choleraesuis. In contrast, IGFBP-3 mRNA relative abundance was increased (P< 0.03) in pigs given Typhimurium compared with control pigs. Muscle IGF-I mRNA was reduced in pigs given Choleraesuis compared with control pigs and pigs given Typhimurium (P< 0.05). Treatment tended to affect muscle IGFBP-3 mRNA (P= 0.10). Oral inoculation of growing pigs with Choleraesuis disrupted feed intake and BW gain, and this was accompanied by decreases in circulating IGF-I and reduced muscle expression of mRNA for IGF-I and IGFBP-3.

We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17β (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17β (Component TE-H). Treatments were arranged as a 2 × 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P< 0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P= 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex × ractopamine × day interaction; P= 0.03). Ractopamine did not affect (P≥ 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine × sex interaction; P= 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P= 0.04) but not in LM (P= 0.99). Ractopamine decreased β2-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of β2-receptor mRNA in LM of heifers was not affected by ractopamine (sex × ractopamine × day interaction; P= 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.

Two studies using beef and calf-fed Holstein cattle were conducted to determine the effect of zilpaterol hydrochloride (ZH) supplementation on the color of strip loin steaks packaged in traditional and modified-atmosphere packaging. Select (USDA) strip loins were obtained from the carcasses of beef (n = 118) or calf-fed Holstein (n = 132) cattle fed ZH (6.8 g/ton on a 90% DM basis) for the last 0, 20, 30, or 40 d of feeding. One portion of the strip loin was moisture enhanced, cut into steaks, and packaged in an atmosphere containing 80% oxygen and 20% carbon dioxide. The remaining portion of the strip loin was vacuum-packaged until further processing. At 14 d postmortem, the vacuum-packaged loins were portioned and packaged in traditional retail packaging. Traditionally packaged and modified-atmosphere-packaged steaks were then placed in retail cases at −1 to 3°C for 5 d and evaluated by both trained and consumer panelists. Instrumental color values and purge loss were also recorded. Zilpaterol hydrochloride duration had no effect on the color and purchase intention scores of consumer panelists for beef and calf-fed Holstein strip loin steaks. Zilpaterol hydrochloride feeding duration had no effect on the color or discoloration scores of trained panelists for enhanced, modified-atmosphere-packaged beef strip steaks. Traditionally packaged beef steaks from cattle treated with ZH for 20 d had more desirable (P< 0.05) lean color scores than steaks from cattle not treated with ZH on d 2, 3, and 4 of display and had similar discoloration scores on d 1, 2, and 3 of display. The color scores of trained panelists for enhanced calf-fed Holstein steaks were more desirable (P< 0.05) for steaks from cattle not treated with ZH than for steaks from cattle treated with ZH for 20 d on d 1, 2, 3, and 4 of display. However, the discoloration scores of trained panelists for enhanced and modified-atmosphere-packaged calf-fed Holstein steaks were similar for steaks from cattle treated with ZH for 0 and 20 d on d 1, 2, and 3 of display. The scores of trained panelists indicated that traditionally packaged steaks from calf-fed Holsteins treated with ZH for 0 d had a darker lean color (P< 0.05) than steaks from ZH-treated cattle on d 1 of display, whereas the lean color scores for ZH treatments of all durations were similar on d 4 of display. The scores of trained panelists indicated that ZH treatment had no effect on the discoloration of traditionally packaged, nonenhanced strip steaks from calf-fed Holsteins. Therefore, feeding ZH to beef or calf-fed Holstein steers had no detrimental effect on the lean color or color stability of strip loin steaks subjected to enhancement, packaged in modified-atmosphere or traditional packaging, and displayed under simulated retail conditions.

This experiment investigated the effects of zilpaterol hydrochloride (ZH) and the steroidal implant Revalor-S (RS; 120 mg of trenbolone acetate and 24 mg of estradiol-17β) on finishing steer performance and the mRNA concentration of β-adrenergic receptors (β-AR) types I and II, and types I, IIA, and IIX myosin heavy chain (MHC) isoforms. A total of 2,279 feedlot steers weighing 426 ± 6.4 kg were administered no implant or RS on d 0, and fed 0 or 8.3 mg of ZH/kg of diet DM during the last 30 d with a 3-d withdrawal. Treatments were randomly assigned to 24 pens (n = 6 pens/treatment). At slaughter, semimembranosus muscle tissue was excised for RNA isolation from 4 carcasses per pen. No interactions were detected for any of the variables measured in the experiment. Administration of ZH during the last 30 d of the feeding period increased (P< 0.01) ADG, G:F, HCW, and LM area; decreased (P< 0.01) 12th-rib fat depth and marbling; and improved (P< 0.01) yield grade. Treatment had no effect on β1-AR mRNA levels, but there was an increase (P= 0.01) in β2-AR mRNA levels due to ZH inclusion. Myosin heavy chain-I (MHC-I) mRNA levels were unaffected by treatment. For MHC-IIA mRNA concentrations, administration of RS tended (P= 0.08) to increase mRNA levels, whereas ZH feeding the last 30 d tended (P= 0.08) to decrease mRNA levels for this isoform of myosin. Feeding ZH the last 30 d before slaughter increased (P< 0.01) mRNA concentrations of MHC-IIX in semimembranosus muscle of steers. These data indicate the combined use of ZH and RS additively contributes to BW and carcass gain in finishing feedlot steers and decreases marbling scores and USDA quality grades. The LM area increased and fat thickness decreased. In addition, ZH feeding changes the mRNA levels of MHC isoforms to a faster, more glycolytic fiber type in bovine skeletal muscle. These changes in mRNA concentrations of MHC isoforms, due to ZH feeding, could be affecting skeletal muscle hypertrophy.

Angiopoietin-like protein 4 (ANGPTL4; also known as fasting-induced adipose factor) is a plasma protein that stimulates oxidation of fatty acids and inhibits fat accumulation. The gastrointestinal tract appears to play an important role in regulating plasma ANGPTL4 concentration in some situations and may be influenced by microbes within the gastrointestinal tract. Our aim was to determine which tissues express ANGPTL4 in the bovine. Rumen, omasum, abomasum, duodenum, jejunum, ileum, colon, pancreas, liver, and subcutaneous adipose tissue samples were collected postmortem from 2 steers. Abundance of ANGPTL4 messenger RNA was quantified by quantitative real-time PCR, and was most abundant in liver and adipose tissue (P< 0.05). We also detected ANGPTL4 messenger RNA throughout the gastrointestinal tract, although its abundance was approximately 10% of that found in liver and adipose tissue. Western blot analysis revealed that ANGPTL4 protein was most abundant in liver and adipose tissue (P< 0.05), but omasal, abomasal, and ileal samples contained at least 60% as much ANGPTL4 protein as the liver and adipose tissue samples, and the protein was detected in all tissues. Finally, cross-sections of the liver, pancreas, and rumen wall were used for indirect immunofluorescent detection of ANGPTL4. Despite the low abundance of ANGPTL4 measured by quantitative real-time PCR and Western blot in ruminal tissue, immunofluorescence demonstrated that expression of ANGPTL4 in ruminal epithelial cells was equivalent to or greater than that in liver hepatocytes. These findings indicate that, as in other species studied, liver and adipose tissue are key sources of ANGPTL4 in cattle. However, the protein was also highly abundant in ruminal epithelium, making it possible that commensal microbes may influence ANGPTL4 synthesis and secretion in the ruminant gastrointestinal tract.

Melengestrol acetate (MGA) has been used in the United States for nearly 40 yr to enhance feedlot heifer performance, yet unequivocal studies have not been conducted to discover the mechanism of action. Our hypothesis was that MGA may induce various populations of muscle-derived cells (MDC) to the adipogenic pathway in both a bovine and murine cell culture model. To determine this, MDC were digested from the semimembranosus muscle tissue of six 14-mo-old crossbred steers. The addition of insulin, oleic acid, and ciglitizone (IOC) with cultured bovine MDC resulted in morphological differences compared with control cultures. Multilocular lipid droplets stained with Oil Red O were seen not only in single MDC, but also in fused myotubes. An increase (P< 0.05) in relative PPARγ messenger RNA (mRNA) levels was measured in MDC incubated with IOC. However, myogenin mRNA levels in MDC incubated with IOC were repressed (P< 0.05) compared with nontreated MDC. Cultures of MDC treated with 10 μMinsulin, 10 μMoleic acid, 10 μMciglitizone, 10 nMestradiol-17β (E2), and 10 nMMGA resulted in cultures with highly distributed lipid droplets not only in single cells, but also in the multinucleated myotubes. Relative C/EBPβ and PPARγ mRNA levels in total RNA isolated from MDC treated with MGA increased (P< 0.05) compared with control cultures. Estradiol treatment had no effect (P> 0.05) on these mRNA levels. The addition of both E2and MGA to MDC increased (P< 0.05) C/EBPβ mRNA levels and tended (P= 0.06) to increase the PPARγ mRNA level. There was no difference (P> 0.10) in relative myogenin mRNA among the control, E2, and MGA treatments. Relative C/EBPβ, PPARγ, and myogenin mRNA levels were investigated in murine C2C12, C3H 10T 1/2, and 3T3-L1 cells. Treatment of cultures with 10 nMMGA increased C/EBPβ levels (P< 0.05) in C2C12 myoblasts and tended (P= 0.08) to increase C/EBPβ levels in 3T3-L1 preadipocytes. These data indicate that populations of cells are present in postnatal skeletal muscle that, under the appropriate stimuli in a culture model, express adipogenic genes and accumulate lipids. In addition, the synthetic progestogen MGA appeared to upregulate the genes necessary for conversion to the adipogenic pathway.

To determine the effects of zilpaterol hydrochloride (ZH; 6.8 g/t on 90% DM basis) feeding duration (0, 20, 30, and 40 d) on Warner-Bratzler shear force (WBSF) of longissimus lumborum (LL), triceps brachii (TB), and gluteus medius (GM) muscles, beef from feeding trials was collected and shipped to participating universities. Animals were slaughtered at commercial processing facilities across the United States. Strip loin, shoulder clod, and top sirloin butt subprimals (IMPS 180, 114, and 184, respectively) were obtained from a portion of USDA Choice and Select grade carcasses for WBSF using standardized procedures and equipment. Feeding ZH increased (P< 0.001) LL WBSF values of USDA Choice and Select steaks. A significant linear contrast existed for both quality grades, indicating increased WBSF values were associated with longer feeding durations. Increased postmortem aging decreased LL WBSF of control and treated steaks. Postmortem aging from 7 to 21 d decreased LL WBSF values by 17.6 and 16.4% for USDA Choice and Select steaks, respectively. The percentage of LL steaks from ZH-supplemented cattle with a WBSF value <4.5 kg was significantly less than control steaks for both quality grades. Postmortem aging from 7 to 21 d postmortem increased (P< 0.001) the percentage of LL Choice and Select steaks with WBSF <4.5 kg for all ZH feeding durations. Feeding ZH for 20, 30, or 40 d increased (P< 0.01) WBSF of USDA Choice TB and GM steaks compared with 0-d controls. Feeding ZH for 0, 20, and 40 d had a similar effect on WBSF of USDA Select GM steaks, and produced lesser values than steaks from cattle fed ZH for 30 d. Feeding ZH for 20, 30, and 40 d had no effect on WBSF values of USDA Select TB steaks. However, the 20-, 30-, and 40-d duration produced WBSF values greater (P< 0.05) than control (0 d) TB steaks. Postmortem aging decreased (P< 0.05) WBSF of USDA Choice and Select TB and GM steaks, but the percentage improvement in WBSF attributed to aging was less than observed for LL steaks. The results of this study indicate feeding ZH increased (P< 0.001) WBSF of LL, TB, and GM. The ZH feeding also decreased (P< 0.01) the percentage of steaks with WBSF <4.5 kg regardless of US quality grade, whereas postmortem aging increased (P< 0.01) the percentage of US Choice and Select steaks with WBSF <4.5 kg. Finally, postmortem aging reduced (P< 0.05) WBSF of steaks from ZH-supplemented beef cattle.

The need to provide consumer data for beef steak tenderness, juiciness, flavor, and overall palatability ratings from zilpaterol hydrochloride (ZH) beef to the processor, retailers, restaurants, and consumers is paramount. Consumer palatability responses were studied for 14- and 21-d aged USDA Choice and USDA Select quality grade beef and USDA Choice calf-fed Holstein New York Strip steaks from cattle that had been fed ZH for 0, 20, and 30 d before slaughter. Strip loins were cut into 2.54-cm-thick New York strip steaks and assigned to a 14- or 21-d aging treatment. The first and fourth steaks were assigned for 14- or 21-d WBSF analysis, and the second, third, fifth, and sixth steaks were reserved for consumer sensory panel evaluation. Warner-Bratzler shear force (WBSF) analysis was conducted at Texas Tech University (TTU, Lubbock), Kansas State University (Manhattan), Oklahoma State University (Stillwater), and West Texas A&M University (Canyon) with values used to sort steaks for consumer evaluation. Slice shear force analysis was performed at TTU on available paired consumer steaks. Consumers (n = 3,007) in 4 metropolitan areas (Baltimore, MD/Washington, DC; Chicago, IL; Los Angeles, CA; and Lubbock, TX) were asked to rate tenderness, juiciness, flavor, and overall acceptability. Consumers were selected to represent a wide range of income, education, and ethnicity at each city. Steaks were cooked to a medium degree of doneness (71°C), cut into 1 cm3pieces, and served warm to consumers. Consumers tasted samples from each of 3 separate steaks from each ZH treatment (0, 20, and 30 d) and within each USDA quality grade and within the 14- and 21-d aging treatments. Steaks were selected to represent the distribution of tenderness for the first, second, and third SD either side of the mean for each treatment. A second calf-fed Holstein consumer study (n = 240) was conducted with consumers eating USDA Choice 14- and 21-d aged steaks from Holstein cattle fed ZH for 0 or 20 d. Steaks from 0- and 20-d ZH treatments were different for tenderness for the 14-d aged USDA Choice and the calf-fed Holstein study groups. No differences were shown for all other 0- and 20-d ZH treatments for tenderness. The 21-d aged USDA Select steaks were improved with aging, which aided in removing the effects of ZH treatment. The ZH treatment of 30 d before slaughter resulted in increased WBSF values and decreased consumer tenderness, juiciness, and overall palatability ratings for 14-d-aged USDA Choice. No differences were shown for tenderness, juiciness, flavor, and overall palatability consumer ratings for 0- and 20-d steaks from 21-d Choice and 14- and 21-d Select quality and aging periods. Overall, USDA Choice Holstein steaks aged 14 and 21 d had differences in tenderness with ZH.

Our objective was to determine the effects of feeding zilpaterol hydrochloride (ZH), a β-agonist, for the final 30 d of the feeding period, with or without a terminal estrogen + trenbolone acetate (TBA) implant (Revalor-S; 24 mg of estradiol-17β and 120 mg of TBA; REV) on meat tenderness and carcass cutout yields. Crossbred steers (n = 2,279) were divided into 6 BW blocks and 24 pens. Within each block, pens were assigned randomly to 1 of 4 treatments: 1) no terminal implant (control); 2) a terminal REV given 91 d before slaughter; 3) no terminal implant plus ZH; and 4) a terminal REV implant plus ZH (REV+ZH). All cattle received Component TE-IS (16 mg of estradiol and 80 mg of TBA) on d 61 of the feeding period. Zilpaterol hydrochloride was added to the diets at a concentration of 8.38 mg/kg (DM basis) during the final 30 d of the feeding period, followed by a 3-d period before slaughter in which ZH was withdrawn from the diet. Carcasses (n = 30/treatment) were selected from the 2,279 cattle and fabricated into subprimal cuts as per Institutional Meat Purchase Specifications. Strip loins were collected, cut into 2.54-cm steaks, and aged 7, 14, and 21 d, after which Warner-Bratzler shear force (WBSF), collagen content, desmin degradation, and muscle fiber diameter measurements were determined. Feeding ZH increased (P< 0.05) yield of the #112A ribeye roll, #116B chuck mock tender, #167A peeled knuckle, #169 top inside round, #171B outside round, #171C eye of round, #180 strip loin, #184 top sirloin butt, and #189A full tenderloin for ZH treatment. Longissimus muscle WBSF at 7, 14, and 21 d postmortem was increased (P< 0.001) with ZH supplementation. Desmin degradation at 7, 14, and 21 d postmortem was not affected with REV or ZH supplementation compared with controls. Zilpaterol hydrochloride had an additive effect with REV on increasing LM fiber diameter (P< 0.001). When fed to cattle that received a terminal implant of REV, ZH potentially increased LM WBSF as a result of induced muscle hypertrophy. During the 21-d aging period, WBSF decreased with aging, suggesting that carcasses from cattle supplemented with ZH might require longer aging time to ensure that acceptable levels of tenderness are reached.

Preselected carcasses (n = 112) from feedlot steers fed zilpaterol hydrochloride (ZH; 8.33 mg/kg, DM basis) in a serial slaughter experiment were evaluated to determine the effects of ZH upon carcass cutability, composition, and tenderness. A 4 × 4 factorial arrangement of treatments in a completely random design was used with days on ZH (0, 20, 30, and 40 d before slaughter with a 3-d withdrawal) and days on the finishing diet (DOF; 136, 157, 177, and 198 d). No relevant ZH duration × slaughter group interactions were detected (P> 0.05) for carcass cutability, composition, or tenderness data. Exposure to ZH increased the lean yield of 22 of the 33 subprimals evaluated with every subprimal within the round showing increased cutability (P≤ 0.04). Carcass fat was decreased, whereas carcass protein and moisture were increased due to ZH (P< 0.01). Lengthening the ZH feeding period did not result in additive gains in subprimal yield or chemical composition (P> 0.05). Warner-Bratzler shear force analysis of the LM indicated that ZH caused a toughening effect (P< 0.01) regardless of the length of the aging period (7, 14, or 21 d). Extending the ZH dose duration caused a linear increase in Warner-Bratzler shear force at 7 (P= 0.06) and 21 d (P< 0.01) of aging. Within 10 min postmortem, samples (n = 48) were collected from the semimembranosus muscle for RNA isolation from 4 randomly selected steers from each treatment within the 157, 177, and 198 d slaughter groups. Feeding ZH did not alter β1- or β2-adrenergic receptor (AR), calpastatin (CAL), IGF-I, or myosin heavy chain (MHC) isoform I mRNA abundance (P> 0.10). There was a ZH duration × DOF interaction (P< 0.01) for the expression of MHC-IIa and -IIx. Expression of MHC-IIa was decreased in every ZH treatment within the 177 and 198 DOF groups (P< 0.02). Expression of MHC-IIx was increased in the 20-d ZH group in the 157 DOF group (P= 0.03), and the 40-d ZH group in the 177 (P= 0.10) and 198 (P= 0.03) DOF groups. There was a tendency for a linear decrease in CAL mRNA abundance as ZH duration increased (P= 0.07), and there was a linear increase in β2-AR (P= 0.03) and CAL (P< 0.01) mRNA abundance as DOF increased. Collectively, the data indicate that ZH may influence net protein turnover by decreasing MHC-IIa mRNA transcription and possibly increasing MHC-IIx. Furthermore, a ZH feeding duration of 20 d appeared to be adequate for capturing lean yield benefits while limiting tenderness losses.

Two experiments evaluated the ability of maternal fatty acid supplementation to alter conceptus and endometrial fatty acid composition. In Exp. 1, treatments were 1) the control, a corn-soybean meal diet; 2) flax, the control diet plus ground flax (3.75% of diet); and 3) protected fatty acids (PFA), the control plus a protected fish oil source rich in n-3 PUFA (Gromega, JBS United Inc., Sheridan, IN; 1.5% of diet). Supplements replaced equal parts of corn and soybean meal. When gilts reached 170 d of age, PG600 (PMSG and hCG, Intervet USA, Millsboro, DE) was injected to induce puberty, and dietary treatments (n = 8/treatment) were initiated. When detected in estrus, gilts were artificially inseminated. On d 40 to 43 of gestation, 7 gilts in the control treatment, 8 gilts in the PFA treatment, and 5 gilts in the flax treatment were pregnant and were slaughtered. Compared with the control treatment, the flax treatment tended to increase eicosapentaenoic acid (EPA: C20:5n-3) in fetuses (0.14 vs. 0.25 ± 0.03 mg/g of dry tissue; P= 0.055), whereas gilts receiving PFA had more (P< 0.05) docosahexaenoic acid (DHA: C22:6n-3) in their fetuses (5.23 vs. 4.04 ± 0.078 mg/g) compared with gilts fed the control diet. Both the flax and PFA diets increased (P< 0.05) DHA (0.60, 0.82, and 0.85 ± 0.078 mg/g for the control, flax, and PFA diet, respectively) in the chorioallantois. In the endometrium, EPA and docosapentaenoic acid (C22:5n-3) were increased by the flax diet (P< 0.001; P< 0.05), whereas gilts receiving PFA had increased DHA (P< 0.001). The flax diet selectively increased EPA, and the PFA diet selectively increased DHA in the fetus and endometrium. In Exp. 2, gilts were fed diets containing PFA (1.5%) or a control diet beginning at approximately 170 of age (n = 13/treatment). A blood sample was collected after 30 d of treatment, and gilts were artificially inseminated when they were approximately 205 d old. Conceptus and endometrial samples were collected on d 11 to 19 of pregnancy. Plasma samples indicated that PFA increased (P< 0.005) circulating concentrations of EPA and DHA. Endometrial EPA was increased (P< 0.001) for gilts fed the PFA diet. In extraembryonic tissues, PFA more than doubled (P< 0.001) the EPA (0.13 vs. 0.32 ± 0.013 mg/g) and DHA (0.39 vs. 0.85 ± 0.05 mg/g). In embryonic tissue on d 19, DHA was increased (P< 0.05) by PFA (0.20 vs. 0.30 ± 0.023 mg/g). Supplementing n-3 PUFA, beginning 30 d before breeding, affected endometrial, conceptus, and fetal fatty acid composition in early pregnancy. Dynamic day effects in fatty acid composition indicate this may be a critical period for maternal fatty acid resources to affect conceptus development and survival.

A series of calix[4]arenes incorporating three or four bidentate diamines or pyridylamines attached at the “upper rim” were synthesized via practical protocols. Proof of structure was obtained in one instance by X-ray crystallography. These molecules are designed for general use as ligands for the preparation of multinuclear active site models of metalloenzymes.

We previously showed that a combined trenbolone acetate (TBA)/estradiol-17β (E2) implant significantly increases IGF-I mRNA levels in the LM of feedlot steers by 28 d after implantation. Here we compare the effects of E2 (25.7 mg), TBA (120 mg), and combined TBA (120 mg)/E2 (24 mg) implants on IGF-I, IGF-I receptor (IGFR-1), estrogen receptor (ER)-α and androgen receptor (AR) mRNA levels in the LM of steers. Twenty yearling crossbred steers with an average initial BW of 421.1 ± 3.6 kg were stratified by BW and randomly assigned to 1 of 4 treatments: 1) nonimplanted, control; 2) implanted with TBA and E2; 3) implanted with E2; or 4) implanted with TBA. Steers were weighed weekly starting on d 0, and muscle biopsy samples were taken from each steer on d 0 (before implantation), 7, 14, and 28. Ribonucleic acid was prepared from each sample and real-time reverse transcription-PCR was used to determine the levels of IGF-I, IGFR-1, ER-α, and AR mRNA. Body weight of implanted steers, adjusted by using d-0 BW as a covariant, tended (P= 0.09) to be greater than that of control steers. On d 7 and 28, IGF-I mRNA levels were greater (58 and 78%, respectively; P< 0.009) in E2-implanted animals than in control steers. Similarly, on d 28 the LM IGF-I mRNA level was 65% greater (P= 0.017) in TBA/E2-implanted steers than in control animals. In contrast, the TBA implant did not increase (P= 0.99) LM IGF-I mRNA levels after 28 d of implantation. Muscle IGFR-1, AR, and ER-α mRNA levels were not different (P> 0.47) in any of the treated groups compared with the control group. These data suggest that E2 is responsible for the increased muscle IGF-I mRNA level observed in steers implanted with a combined TBA/E2 implant.

Two experiments evaluated the effects of conventional and natural feedlot management systems (MS) on ractopamine-HCl (RAC) response in yearling steers. Feedlot performance, carcass characteristics, skeletal muscle gene expression, and circulating IGF-I concentrations were measured. The conventional system included a combined trenbolone acetate and estradiol implant, Revalor-S (IMP), as well as monensin-tylosin feed additives (IA). Treatments were arranged in a 2 × 2 factorial and included: 1) natural (NAT): no IMP-no IA, no RAC; 2) natural plus (NAT+): no IMP-no IA, RAC; 3) conventional (CON): IMP-IA, no RAC; and 4) conventional plus (CON+): IMP-IA, RAC. In Exp. 1, one hundred twenty crossbred steers (initial BW = 400 ± 26 kg) were allotted randomly to treatment in a randomized complete block design (BW was blocking criteria); pen was the experimental unit. In Exp. 2, twenty-four individually fed crossbred steers (initial BW = 452 ± 25 kg) were used in a randomized complete block design (BW was blocking criteria) and assigned to the same treatments as Exp. 1, with 6 steers/treatment. In Exp. 2, serum was harvested on d 0 and 31 and within the 28-d RAC feeding period, at d 0, 14, and 28. Longissimus biopsy samples were taken on d 0, 14, and 28 of the RAC feeding period for mRNA analysis of β-adrenergic receptors and steady-state IGF-I mRNA. In Exp. 1, ADG, G:F, final BW, and HCW were greatest for CON+ (P< 0.01). During the final 37 d, RAC increased ADG (P= 0.05) and increased overall G:F (P= 0.02). Marbling score was reduced (P= 0.02), and yield grade was improved with RAC (P= 0.02), but RAC did not affect dressing percentage (P= 0.96) or HCW (P= 0.31). In Exp. 2, MS × RAC interactions were detected in ADG and G:F the last 28 d, overall ADG and overall G:F, final BW, and HCW (P< 0.01). Dressing percentage, yield grade, and marbling score were not altered by MS or RAC (P> 0.10). Circulating IGF-I concentration was increased on d 31 by the conventional MS, and concentration was greater throughout the study than NAT steers (P< 0.01). Circulating IGF-I concentrations were not changed by RAC (P= 0.49). Abundance of β1-AR mRNA tended to increase (P= 0.09) with RAC, but RAC did not affect β2-AR, β3-AR, or IGF-I mRNA (P> 0.40). Management system did not affect β1-AR, β2-AR, β3-AR, or IGF-I mRNA (P> 0.18), yet a trend (P= 0.06) for MS × RAC for β2-AR mRNA was detected. These results indicate that response to RAC is affected by feedlot management practices.

Proanthocyanidins (PACs) are naturally occurring polymers derived from higher plants and they have recently been associated with several potential positive health benefits such as antibacterial, chemotherapeutic, and anti-atherosclerotic activities. Here we report on the binding of PACs from cranberries, tea, and grapes to lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria. LPS is the cause of several human illnesses, including sepsis and toxic shock syndrome. We show that in the case of cranberries, the majority of the LPS-binding activity is contained within a PAC fraction composed of polymers with an average degree of polymerization of 21. This PAC fraction modestly inhibits the binding of LPS to the surface of mammalian cells expressing the full complement of LPS receptors while it significantly abrogates the cellular internalization of LPS. Our results demonstrate PACs to be a new class of LPS-binding compound with potential utility in the removal of LPS from potable water sources and pharmaceutical preparations. [ABSTRACT FROM AUTHOR]

Postnatal skeletal muscle growth is a result of hypertrophy of existing skeletal muscle fibers in food producing animals. Accumulation of additional nuclei, as a source of DNA, to the multinucleated skeletal muscle fiber aids in fiber hypertrophy during periods of rapid skeletal muscle growth. Muscle satellite cells are recognized as the source of nuclei to support muscle hypertrophy. Exogenous growth-enhancing compounds have been used to modulate growth rate and efficiency in meat animals for over a half century. In cattle, these compounds enhance efficiency of growth by preferentially stimulating skeletal muscle growth compared with adipose tissue. There are 2 main classes of compounds approved for use in cattle in the United States, anabolic steroids and β-adrenergic agonists (β-AA). Administration of both trenbolone acetate and estradiol-17β, as implants, increased carcass protein accumulation 8 to 10% in yearling steers. Muscle satellite cells isolated from steers implanted with trenbolone acetate/ estradiol-17βhad a shorter lag phase in culture compared with satellite cells isolated from control steers. Collectively, these data indicate that activation, increased proliferation, and subsequent fusion of satellite cells in muscles of implanted cattle may be an important mechanism by which anabolic steroids enhance muscle hypertrophy. Oral administration of β-AA to ruminants does not alter DNA accumulation in skeletal muscle over a typical feeding period (28 to 42 d). Enhanced muscle hypertrophy observed due to β-AA feeding occurs by direct, receptor-mediated changes in protein synthesis and degradation rates of skeletal muscle tissue. Proper timing of anabolic steroid administration when coupled with β-AA feeding could result in a synergistic response in skeletal muscle growth due to the effects of anabolic steroids at increasing satellite cell activity, which then can support the rapid hypertrophic changes of the muscle fiber when exposed to β-AA. At the same time each of these classes of compounds are stimulating lean tissue deposition, they appear to repress adipogenesis in meat animals. Increased knowledge of the mechanism by which growth promotants regulate lean tissue deposition and adipogenesis in meat animals will allow for effective application of these techniques to optimize lean tissue growth and minimize the negative effects on meat quality.

Forty crossbred wethers (BW = 28.7 kg) were used to evaluate the effects on LM lipid composition of diets containing high and low levels of vitamin A. Four treatments arranged as a 2 × 2 factorial with a completely random design were investigated: backgrounding (BG) and finishing (FN) with no supplemental vitamin A (LL); BG with no supplemental vitamin A and FN with high vitamin A (6,600 IU/kg of diet, as fed) supplementation (LH); BG with high vitamin A supplementation and FN with no vitamin A supplementation (HL); and BG and FN with high vitamin A (HH) supplementation. Diets included cracked corn (62.4%), soybean meal (16.0%), cottonseed hull pellets (14.8%), and supplement (7%), and contained <100 IU of vitamin A/kg (as fed) from carotenes before vitamin A was added. During the BG period (d 1 to 56), feed intake was restricted to achieve 0.22 kg of ADG. During the FN period (d 57 to 112), lambs consumed the same diet ad libitum. Lambs were weighed every 14 d, and blood was sampled every 28 d to evaluate changes in serum fatty acids and vitamin A levels. Lambs were slaughtered after 112 d. Lipid composition was determined for liver and LM. There were no treatment differences (P> 0.05) in feed intake, ADG, or final BW. Carcass weights were not affected by vitamin A treatment (P> 0.20), although backfat thickness tended to be different between HL and LL lambs (0.80 vs. 0.64 cm, respectively; P= 0.08). Carcasses from the HH group had greater (P< 0.05) marbling scores than those from the LL group (514 vs. 459) and had 25.8% more extractable intramuscular lipids (3.88 vs. 3.08% for HH and LL, respectively; P< 0.05); the LH and HL treatments were intermediate. Interestingly, the LL group had the greatest increase in serum fatty acids throughout the experimental period (change of 127 vs. 41 μg/g for LL and HH, respectively; P< 0.01). The degree of saturation of fatty acids was not affected by treatment (P= 0.18) in the serum but was affected in the longissimus thoracis fat. Oleic acid increased and linoleic acid decreased in the longissimus thoracis of HH-treated lambs (P< 0.02). These data suggest that increases in total intramuscular lipids may be achieved with high levels of vitamin A supplementation for 112 d in young lambs.

Two experiments were conducted to investigate the effects of ractopamine-HCl (RAC) and implant strategy or days on feed (DOF) on feedlot performance and expression of β-adrenergic receptors (AR). In Exp. 1, 1,147 feedlot heifers weighing 282 ± 3 kg were used with implant treatments of Revalor-200 (R200) at arrival, or Revalor-IH at arrival with reimplantation with Finaplix-H on d 58 (RF). Ractopamine (0 vs. 200 mg/d) was fed the last 28 d in both experiments. Treatments were randomly assigned to 16 pens. At slaughter, semimembranosus muscle tissue was excised for RNA isolation. Ractopamine administration increased (P< 0.05) ADG, G:F, HCW, and LM; decreased (P< 0.05) 12th rib fat depth; and improved (P< 0.05) yield grade. There was no effect (P> 0.10) on the expression of β1-AR mRNA; however, there was a tendency (P= 0.10) for RAC feeding to increase β2-AR mRNA levels. For β3-AR mRNA, there was an implant by RAC interaction (P= 0.05), with RAC numerically increasing β3-AR mRNA in heifers implanted with RF, but a decrease (P< 0.05) in expression in heifers implanted with R200. Ractopamine also decreased (P< 0.05) IGF-I mRNA in heifers implanted with RF. In Exp. 2, 2,077 heifers were used to investigate the effects of RAC and DOF. Days on feed were 129, 150, and 170, and RAC was administered the last 28 d. Ractopamine improved (P< 0.05) G:F, but had no other effects (P> 0.05) on performance. Average daily gain decreased (P< 0.05) as DOF increased. Hot carcass weight, LM area, 12th rib fat, G:F, calculated yield grade, and marbling score increased (P< 0.05) and the percentage of KPH fat decreased (P< 0.05) as DOF increased. These data aid in our understanding of the effects of steroidal implants, DOF, and RAC administration in feedlot heifers.

A total of 59 gilts (BW = 137.7 kg) from 3 breeding groups were used to assess the effects of feeding L-carnitine during gestation on gilt growth characteristics, blood metabolites, and uterine and chorioallantoic expression of IGF axis components at d 40, 55, and 70 of gestation. Experimental treatments were arranged in a 2 × 3 factorial, with main effects of added L-carnitine (0 or 50 ppm) and day after initial breeding (d 40, 55, or 70 of gestation). All gilts received a constant feed allowance of 1.75 kg/d and a top-dress containing 0 or 50 ppm of L-carnitine beginning on the first day of breeding through the assigned day of gestation. No dietary treatment differences were observed for gilt BW, backfat, or estimated protein or fat mass at any day of gestation. No differences were observed in circulating total and free carnitine at breeding, but concentrations increased (P< 0.01) as day of gestation increased for gilts fed diets containing L-carnitine compared with those fed the control diet. Maternal IGF-I concentration decreased (P< 0.01) from d 0 to 70 for all gilts, with no differences between treatments. Insulin-like growth factor binding protein-3 mRNA (P= 0.05) and IGFBP-5 mRNA (P= 0.01) increased in the endometrium of gilts supplemented with L-carnitine. These data demonstrate that L-carnitine supplementation and day of gestation alter the expression of the IGF axis by changing the expression of IGFBP at the fetal-maternal interface in swine. These changes in the IGF axis at the fetal maternal interface may aid in determining the reasons for the effects of L-carnitine on reproductive traits.

The most common Salmonellaserovars causing clinical disease in pigs are Salmonella entericaserovars Typhimurium (Typhimurium) and Choleraesuis. Given that the swine host-adapted serovar Choleraesuis has been reported to cause systemic disease, a different disease outcome from that of Typhimurium, our working hypothesis was that this serovar would likely engage systemic immune-inflammatory mechanisms, resulting in elevated systemic cytokine secretion. Forty-eight weaned pigs were blocked by BW and sex, and randomly allotted to 1 of 3 treatments in a 14-d study. Each treatment had 8 replicates (pens), with 2 pigs/pen. The treatments consisted of a negative control and pigs repeatedly fed 108cfu of Typhimurium or Choleraesuis. On d 0, the pigs were fed Choleraesuis or Typhimurium in dough balls, and the bacteria were refed twice weekly throughout the experiment. Control pigs received dough balls without bacteria. All pigs were housed in temperature-controlled rooms under constant lighting and were fed a standard corn-soybean meal-based nursery diet. Pig BW and feed disappearance were used to determine ADG, ADFI, and G:F. Rectal temperatures were obtained daily from 1 pig/pen beginning 2 d before the first bacterial feeding through d 7 using rapid-response digital thermometers. Serum was collected on d 0, 7, and 14 from a single pig/pen for analysis of IGF-I, tumor necrosis factor-α , and IL-1β. There was no change in the rectal temperature of the control or the Typhimurium-challenged pigs (compared with d 0) or when comparing Typhimurium-challenged pigs with control animals. In contrast, pigs fed Choleraesuis had increased rectal temperatures beginning on d 2 and continuing through d 7 (P< 0.05), with the greatest elevation on d 3 (P< 0.001) compared with the control pigs. Average daily gain and ADFI of pigs challenged with Typhimurium did not differ from those of the control animals. Pigs fed Choleraesuis had a 25% reduction in ADG (P< 0.0001) and ADFI (P< 0.002) compared with the control pigs. On d 7, pigs fed Choleraesuis had reduced serum IGF-I compared with control (P< 0.01) or Typhimurium-challenged pigs (P= 0.01). Bacterial feeding did not affect serum tumor necrosis factor-α or IL-1β compared with control pigs at any time throughout the experiment. We conclude that repeated exposure of weaned pigs to Choleraesuis reduced growth performance in the absence of changes in systemic inflammatory cytokines.

Yearling steers (n = 2,552; 314 kg of initial BW) were used to evaluate the effects of ractopamine-HCl (RAC) and days on feed on performance, carcass characteristics, and skeletal muscle gene expression in finishing steers. Treatment groups included serial slaughter dates of 150, 171, or 192 d on feed. Within each slaughter date, steers either received RAC (200 mg/steer) daily for the final 28 d or were not fed RAC. All steers were initially implanted with Revalor-IS and were reimplanted with Revalor-S after 75 d on feed. At slaughter, muscle samples from the semimembranosus were collected for mRNA analysis of the β-adrenergic receptors (β-AR). Ractopamine administration increased (P< 0.05) ADG, G:F, and HCW and increased (P= 0.08) LM area. Ractopamine did not affect the dressing percentage, USDA yield grade, or quality grade (P> 0.3). There was no change in overall feed intake across the entire feeding period; however, feed intake was increased during the 28-d period during which the steers were fed RAC (P≤ 0.05). Greater days on feed decreased (P< 0.05) ADG, G:F, DMI, and the number of yield grade 1 and 2 carcasses. Also, greater days on feed increased (P< 0.05) HCW, dressing percentage, and the number of prime and choice carcasses, as well as the number of yield grade 4 and 5 carcasses. Increasing days on feed decreased (P< 0.05) the abundance of β1-AR and β3-AR mRNA and increased (P< 0.05) the abundance of β2-AR mRNA in skeletal muscle samples obtained at slaughter. Ractopamine had no effect (P> 0.10) on the abundance of β1-AR or β3-AR mRNA, but tended (P= 0.09) to increase β2-AR mRNA. Additional time-course studies with primary muscle cell cultures revealed that advancing time in culture increased (P< 0.001) β2-AR mRNA but had no effect (P> 0.10) on β1-AR or β3-AR mRNA. We conclude that days on feed and RAC are affecting β-AR mRNA levels, which could, in turn, impact the biological response to RAC feeding in yearling steers.

In vitro experiments were performed to investigate the effects of melengestrol acetate (MGA) or progesterone (P4) on bovine muscle satellite cells and C2C12myoblasts. Addition of MGA at physiological and supraphysiological concentrations resulted in a dose-dependent decrease (P< 0.05) in DNA synthesis as measured by 3H]-thymidine incorporation (TI). Similarly, P4 addition (0.01 nM) reduced (P< 0.05) TI. Addition of MGA (10 nM) increased (P< 0.05) IGF-I mRNA abundance but did not affect myogenin mRNA. Progesterone addition (10 nM) increased myogenin mRNA abundance (P< 0.05). In C2C12cultures, P4 addition resulted in a dose-dependent decrease in TI. The antiprogestin RU486, in combination with MGA or P4, also resulted in reduced (P< 0.05) TI. Treatment with RU486 alone had a negative effect (P< 0.05) on TI that was similar to the progestins. Treatment of C2C12myoblasts with MGA (100 nM) resulted in an increase (P< 0.05) in myogenin mRNA. These studies suggest that progestins may reduce satellite cell proliferation, ultimately affecting carcass composition.

The effects of L-carnitine on porcine fetal growth traits and the IGF system were determined. Fourth-parity sows were fed a gestation diet with either a 50-g top dress containing 0 (control, n = 6) or 100 mg of L-carnitine (n = 6). At midgestation, fetuses were removed for growth measurements, and porcine embryonic myoblasts (PEM) were isolated from semitendinosus. Real-time quantitative PCR was used to measure growth factor messenger RNA (mRNA) levels in the uterus, placenta, muscle, hepatic tissue, and cultured PEM. A treatment × day interaction (P= 0.02) was observed for maternal circulating total carnitine. Sows fed L-carnitine had a greater (P= 0.01) concentration of total carnitine at d 57 than control sows. Circulating IGF-I was not affected (P= 0.55) by treatment. Supplementing sows with L-carnitine resulted in larger (P= 0.02) litters (15.5 vs. 10.8 fetuses) without affecting litter weight (P= 0.07; 1,449.6 vs. 989.4 g) or individual fetal weight (P= 0.88) compared with controls. No treatment effect was found for muscle IGF-I (P= 0.36), IGF-II (P= 0.51), IGFBP-3 (P= 0.70), or IGFBP-5 (P= 0.51) mRNA abundance. The abundance of IGF-I (P= 0.72), IGF-II (P= 0.34), and IGFBP-3 (P= 0.99) in hepatic tissue was not influenced by treatment. Uterine IGF-I (P= 0.46), IGF-II (P= 0.40), IGFBP-3 (P= 0.29), and IGFBP-5 (P= 0.35) mRNA abundance did not differ between treatments. Placental IGF-I (P= 0.30), IGF-II (P= 0.18), IGFBP-3 (P= 0.94), and IGFBP-5 (P= 0.42) mRNA abundance did not differ between treatments. There was an effect of side of the uterus for IGF-I (P= 0.04) and IGF-II (P= 0.007) mRNA abundance; IGF-I mRNA abundance was greater in the left uterine horn than in the right uterine horn (0.14 and 0.07 relative units, respectively). Placental IGF-II mRNA abundance was greater (P= 0.007) in the left than in the right uterine horn (483.5 and 219.59, respectively). The abundance of IGFBP-3 was not affected by uterine horns in either uterine (P= 0.66) or placental (P= 0.13) tissue. There was no treatment difference for IGF-I (P= 0.31) or IGFBP-5 (P= 0.13) in PEM. The PEM isolated from sows fed L-carnitine had decreased IGF-II (P= 0.02), IGFBP-3 (P= 0.03), and myogenin (P= 0.04; 61, 59, and 67%, respectively) mRNA abundance compared with controls. These data suggest that L-carnitine supplemented to gestating sows altered the IGF system and may affect fetal growth and development.

In recent years, we have sought to understand how disparate endocrine and immune signals converge in response to Salmonella entericaserovar Typhimurium (ST) to affect growth and the IGF system in the nursery pig. The enteric pathogen ST interacts with gut epithelium to rapidly upregulate the chemoattractive chemokines IL-8 and chemokine ligand-20, and to selectively affect toll-like receptors. Activation of these components of the innate immune system seems to confine the immune response largely to the gut mucosa and mesenteric lymph nodes, as evidenced by the lack of systemic elevation of proinflammatory cytokines. Despite the apparent restriction of proinflammatory signals to the gut-associated lymphoid tissue, ST provokes peripheral sequelae consistent with danger signaling, including the febrile response and activation of the adrenal axis. In addition, pigs undergoing ST-induced febrile responses experience a consistent period of inappetence that is independent of changes in leptin. Moreover, this period of decreased intake is invariably accompanied by an unmistakable decrease in serum IGF-I and, less consistently, with parallel reductions in circulating IGFBP-3. More recently, we characterized changes in expression of components of the IGF system within skeletal muscle of pigs undergoing ST-associated enteric disease. Despite the characteristic decrease in circulating IGF-I, the relative abundance of skeletal muscle IGF-I and IGFBP-3 mRNA was unaffected by ST. However, mRNA for IGFBP-5 was decreased in the skeletal muscle of ST-challenged pigs, suggesting a possible effect of the enteric disease on IGF availability. Taken together, oral challenge with ST engages elements of the mucosal innate immune system that seem to contain the spread of systemic proinflammatory cytokine signals. Even so, ST challenge is associated with parallel changes in both systemic and local IGF systems that may affect pig growth.