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The objectives of this study were to describe a system to assess KPH fat by using real-time ultrasound (RTU) and to develop equations to predict total physical separable internal fat (IFAT) based on ultrasound measurements. Data for this study were obtained from 24 Angus steers fed either hay- or corn-based diets during the backgrounding phase. Steers were serially slaughtered in 3 groups: at weaning (baseline), then at 4 and 8 mo after weaning. A fourth group was composed of 4 steers from the hay-fed group that were slaughtered at approximately 10 mo after weaning. The RTU measurements were collected every 2 mo, with a preslaughter scan approximately 7 d before the slaughter time. The RTU measurements consisted of 12th- to 13th-rib backfat thickness, 12th to 13th ribeye area, percentage of intramuscular fat, and kidney fat depth, which was measured in a cross-sectional image collected between the first lumbar vertebra and the 13th rib. For kidney fat, the ultrasound probe was placed on the flank region approximately 15 cm from the midline of the animal. Images were stored in the ultrasound console, and measurements were taken between the ventral part of the iliocostalis muscle and the end of the KPH fat at the chute side. The relationship between carcass and ultrasound measurements in the depths of kidney fat (cKFd and uKFd, respectively) had an r(2) of 0.93, with a root mean square error (RMSE) of 1.14 cm. An allometric regression between carcass KPH weight (cKPHwt) and cKFd was identified, and the untransformed regression had an r(2) of 0.96. The linear regression between total IFAT and cKPHwt had an r(2) of 0.97, with an RMSE of 2.67 kg. Therefore, a system was developed to predict IFAT from uKFd measurements by combining these equations. Additionally, a single linear regression between IFAT and uKFd measurements was developed (r(2) = 0.89, RMSE = 5.32 kg). Even though the system of equations had a lower RMSE of prediction and greater r(2) compared with the single linear regression (4.80 vs. 5.10 kg and 0.91 vs. 0.89, respectively), there was no difference between these methods in predicting IFAT (P = 0.4936) by using a pairwise mean square error of prediction analysis. Our results indicated that uKFd measurements can accurately and precisely predict the cKFd of steers consuming either high concentrate or forage rations. The results also showed that cKFd is highly correlated with cKPHwt, which can be used to estimate total IFAT. More research is needed to further evaluate this technique with different feeding strategies, breeds, and sexes.

A comparative slaughter trial was conducted with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg of BW, to assess the net requirements of protein and energy for growth and maintenance. Three cattle from each group (i.e., steers, bulls, and heifers) were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves were randomly assigned to 1 of 3 treatments: maintenance (diet containing 70% of DM as corn silage fed at 1.2% of BW daily) or concentrate at 0.75 or 1.5% of BW daily with corn silage available for ad libitum consumption. The diets were isonitrogenous (2% N, DM basis). The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict the maintenance requirements for NE and net protein (MRNE and MRNP, respectively) and the growth requirement for NE and net protein (GRNE and GRNP, respectively). After 84 d of growth, the cattle were slaughtered. The cleaned gastrointestinal tracts, organs, carcasses, heads, hides, tails, feet, blood, and tissues were weighed to measure empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal within a period, DMI was measured daily and samples of feces were collected to determine diet digestibility. There were no differences in MRNE (P = 0.06) among groups. The combined data indicated a MRNE of 71.2 kcal x kg(-0.75) of EBW x d(-1), with a partial efficiency of use of ME to NE(m) of 0.71. The partial efficiency of use of ME to NE for growth was 0.54 for bulls, 0.47 for steers, and 0.54 for heifers. The GRNE for steers and heifers were similar (P = 0.15) but were 18.7% greater (P = 0.03) for steers and heifers than for bulls. The MRNP did not differ among groups and averaged 2.53 g of CP x kg(-0.75) of EBW x d(-1). Likewise, GRNP was not different among groups. The percentage of retained energy deposited as protein (RE(p)) increased as the content of retained energy in the gain (RE(c), Mcal/kg of empty body gain) decreased. The RE(p) equation of the pooled data was 46.5 x e(-0.2463 x RE(c)). We conclude that the energy requirement of crossbred Bos indicus x Bos taurus for maintenance might be less than that of purebred Bos taurus and that RE(p) is nonlinearly, negatively correlated with RE(c). The GRNE was less for bulls than for steers and heifers. However, we found no differences in MRNE, MRNP, and GRNP for bulls, steers, and heifers of Nellore x Red Angus crossbreds.

Meat production by goats has become an important livestock enterprise in several parts of the world. Nonetheless, energy and protein requirements of meat goats have not been defined thoroughly. The objective of this study was to determine the energy and protein requirements for maintenance and growth of 34 (3/4) Boer x (1/4) Saanen crossbred, intact male kids (20.5 +/- 0.24 kg of initial BW). The baseline group was 7 randomly selected kids, averaging 21.2 +/- 0.36 kg of BW. An intermediate group consisted of 6 randomly selected kids, fed for ad libitum intake, that were slaughtered when they reached an average BW of 28.2 +/- 0.39 kg. The remaining kids (n = 21) were allocated randomly on d 0 to 3 levels of DMI (treatments were ad libitum or restricted to 70 or 40% of the ad libitum intake) within 7 slaughter groups. A slaughter group contained 1 kid from each treatment, and kids were slaughtered when the ad libitum treatment kid reached 35 kg of BW. Individual body components (head plus feet, hide, internal organs plus blood, and carcass) were weighed, ground, mixed, and subsampled for chemical analyses. Initial body composition was determined using equations developed from the composition of the baseline kids. The calculated daily maintenance requirement for NE was 77.3 +/- 1.05 kcal/kg(0.75) of empty BW (EBW) or 67.4 +/- 1.04 kcal/kg(0.75) of shrunk BW. The daily ME requirement for maintenance (118.1 kcal/kg(0.75) of EBW or 103.0 kcal/kg(0.75) of shrunk BW) was calculated by iteration, assuming that the heat produced was equal to the ME intake at maintenance. The partial efficiency of use of ME for NE below maintenance was 0.65. A value of 2.44 +/- 0.4 g of net protein/kg(0.75) of EBW for daily maintenance was determined. Net energy requirements for growth ranged from 2.55 to 3.0 Mcal/kg of EBW gain at 20 and 35 kg of BW, and net protein requirements for growth ranged from 178.8 to 185.2 g/kg of EBW gain. These results suggest that NE and net protein requirements for growing meat goats exceed the requirements previously published for dairy goats. Moreover, results from this study suggest that the N requirement for maintenance for growing goats is greater than the established recommendations.

Effects of 2-nitro-1-propanol, 2-nitroethanol, nitroethane, and 2-nitro-methyl-propionate (0, 10, and 20 mM) on growth of Campylobacter jejuni were tested during culture in Bolton broth adjusted to pH 5.6, 7.0, or 8.2. The nitrocompounds were similarly tested against C. coli but at pH 8.2 only. Viable cell counts measured during incubation revealed main effects (P < 0.05) of all nitrocompounds on the survivability of C. jejuni. An effect of pH (P < 0.05) on the survivability of C. Jejuni during incubation with nitrocompounds was observed, with greater inhibition observed at pH 8.2 than at pH 5.6 or 7.0 for nitroethane, 2-nitro-l-propanol, and 2-nitroethanol, but not for 2-nitro-methyl-propionate, which showed greatest inhibition at pH 5.6. Except for 2-nitro-methyl-propionate, which was ineffective, all nitrocompounds elicited similar effects on C. coli. The effect of nitroethane and 2-nitro-l-propanol (10 mM) on naturally occurring Campylobacter was investigated during incubation of porcine fecal suspensions, where Campylobacter concentrations decreased more rapidly (P < 0.05) in suspensions with added 2-nitro-l-propanol than in unsupplemented or nitroethane-supplemented suspensions, thus reiterating the superior inhibitory effect of 2-nitro-l-propanol.

Anti-tick treatments are often applied concurrent to routine livestock management practices with little regard to actual infestation levels. Prescription treatments against ticks on grazing cattle would be facilitated by non-invasive detection methods. One such method is fecal near infrared spectroscopy (NIRS). Four studies utilizing cattle ( Bos spp.) and one with horses ( Equus caballus ) fed varying diets and infested with either Amblyomma americanum , A. maculatum , A. cajennense or Dermacentor albipictus were conducted to determine the ability of fecal NIRS to identify samples from animals with (High stress) and without (Low stress) a tick burden. Discriminant analysis of each individual trial resulted in R 2 > 0.80. Similar analyses utilizing all combinations of four studies, predicting group membership in the remaining study, yielded R 2 > 0.80, but correct determinations for Low and High tick stress samples of only 53.4 and 60.1%, respectively. All five trials were combined and a random 10 or 25% of the samples were removed from the calibration. As in the previous calibrations, a high degree of discrimination was achieved ( R 2 > 0.89). The validation samples were correctly identified at 91.7% for Low stress and 96.3% for High stress, respectively. Difficulties in detecting differences in fecal samples due to confounding effects of trial were overcome by combining calibration sets. Overall, differences in fecal NIR spectra apparently due to tick stress were accurately detected across diet, host species, and tick species.

Nitroethane inhibits the growth of certain zoonotic pathogens such as Campylobacter and Salmonella spp., foodborne pathogens estimated to cause millions of human infections each year, and enhances the Salmonella- and Escherichia coli-killing effect of an experimental chlorate product being developed as a feed additive to kill these bacteria immediately pre-harvest. Limited studies have shown that nitroethane inhibits ruminal methane production, which represents a loss of 2-12% of the host's gross energy intake and contributes to global warming and destruction of the ozone layer. The present study was conducted to assess the effects of 14-day oral nitroethane administration, 0 (0X), 80 (1X) or 160 (2X)mg nitroethane/kg body weight per day on ruminal and fecal E. coli and Campylobacter, ruminal and fecal methane-producing and nitroethane-reducing activity, whole animal methane emissions, and ruminal and fecal fermentation balance in Holstein steers (n=6 per treatment) averaging 403+/-26 (SD) kg BW. An experimental chlorate product was fed the day following the last nitroethane administration to determine effects on E. coli and Campylobacter. The experimental chlorate product decreased (P0.001) fecal, but not ruminal (P0.05) E. coli concentrations by 1000- and 10-fold by 24 and 48 h, respectively, after chlorate feeding when compared to pre-treatment concentrations (5.7 log(10) colony forming units/g). No effects (P0.05) of nitroethane or the experimental chlorate product were observed on fecal Campylobacter concentrations; Campylobacter were not recovered from ruminal contents. Nitroethane treatment decreased (P0.01) ruminal (8.46, 7.91 and 4.74+/-0.78 micromol/g/h) and fecal (3.90, 1.36 and 1.38+/-0.50 micromol/g/h) methane-producing activity for treatments 0X, 1X and 2X, respectively. Administration of nitroethane increased (P0.001) nitroethane-reducing activity in ruminal, but not fecal samples. Day of study affected ruminal (P0.0001) but not fecal (P0.05) methane-producing and nitroethane-reducing activities (P0.01); treatment by day interactions were not observed (P0.05). Ruminal accumulations of acetate decreased (P0.05) in 2X-treated steers when compared with 0X- and 1X-treated steers, but no effect (P0.05) of nitroethane was observed on propionate, butyrate or the acetate to propionate ratio. Whole animal methane emissions, expressed as L/day or as a proportion of gross energy intake (%GEI), were unaffected by nitroethane treatment (P0.05), and were not correlated (P0.05) with ruminal methane-producing activity. These results demonstrate that oral nitroethane administration reduces ruminal methane-producing activity but suggest that a microbial adaptation, likely due to an in situ enrichment of ruminal nitroethane-reducing bacteria, may cause depletion of nitroethane, at least at the 1X administration dose, to concentrations too low to be effective. Further research is warranted to determine if the optimization of dosage of nitroethane or related nitrocompouds can maintain the enteropathogen control and anti-methanogen effect in fed steers.

We hypothesized that dietary supplementation of (n-6) plus (n-3) PUFA during late gestation would increase uncoupling protein-1 (UCP1) gene expression and thereby increase thermogenic capacity of newborn lambs. Thirty twin-bearing ewes were fed rumen-protected fat (2, 4, or 8%) high in saturated and monounsaturated fatty acids (SMFA) or high in (n-6) and (n-3) PUFA. Lambs (n = 7-10 per ewe treatment group) were placed in a cold chamber at 0 degrees C for 2 h. Rectal temperature was higher at birth and increased more with cold exposure in lambs from ewes fed 2 or 4% supplemental fat than in lambs from ewes fed 8% SMFA (fat type x fat level interaction, P = 0.001). Cytochrome c oxidase activity was greatest in brown adipose tissue (BAT) lambs from ewes fed 2% SMFA or 4% PUFA (fat type x fat level interaction, P = 0.01). BAT of lambs from ewes fed 2 or 4% PUFA had nearly 7-fold more (P = 0.05) UCP1 mRNA than BAT of lambs from ewes fed 8% PUFA. UCP1 expression decreased by over 80% by 24 h of age. Supplementation of 8% fat tended to depress palmitate esterification into lipids (P = 0.07) and decreased palmitate oxidation (P = 0.003) in lamb BAT in vitro, especially in those lambs from ewes fed 8% SMFA. Thus, supplementing the diets of ewes with 8% SMFA depressed cold tolerance in newborn lambs, which was reflected in their decreased ability to oxidize fatty acids in vitro.

This study was conducted to develop a multiple trait index including residual feed intake with the objective to improve net feedlot revenue in market progeny of tested bulls. The selection objective was defined as H = v 1 E 1 + v 2 E 2 + v 3 E 3 , where aggregate genetic merit (H) was a linear function of daily DMI (E 1 , kg/d), ADG (E 2 , kg/d), and slaughter BW (E 3 , kg) of progeny. Regression of steer (n = 426) net revenue on traits in the objective yielded the vector of economic weights ( v ) with elements v 1 = $−21.49, v 2 = $183.73, and v 3 = $0.27. The selection criterion was defined as I = b 1 X 1 + b 2 X 2 +b 3 X 3 , where index value (I) was a linear function of residual feed intake (X 1 , kg/d), ADG (X 2 , kg/d), and adjusted 365-d BW (X 3 , kg) phenotypes of tested bulls. Residual feed intake was defined as the difference between actual DMI (kg/d) and that predicted by phenotypic regression (R 2 = 0.69, residual SD = 0.58 kg/d) of daily DMI on ADG, metabolic mid-test BW, and on-test gain in ultrasound subcutaneous fat depth and longissimus area in Angus bulls (n = 99). The matrix of genetic covariances of criterion traits with objective traits ( G ) was estimated from recent literature and the phenotypic matrix of (co)variances among criterion traits ( P ) was estimated from Angus bulls with test data. Criterion weights were obtained from the solution to b = P 1 Gv with elements b 1 = −10.12, b 2 = 24.79, and b 3 = −0.09. Index values ofbulls adjusted to a mean of 100 (SD = 7.81) ranged from 80.1 to 115.7. Bull ADG, residual feed intake, and 365-d BW accounted for 38, 48, and 14% of the variance in index values, respectively. Phenotypic correlation estimates (P 0.89) with 365-dBW.

The effects of feed or water administration of experimental chlorate preparations on recovery of generic Escherichia coli and E. coli O157:H7 from the gut, hide and carcasses of feedlot cattle were tested. Sixty-four naturally colonized cattle were randomly assigned to one of four feed treatments with or without a 12 h chlorate-containing water treatment. An analysis of variance revealed a main effect of feed treatment ( P = 0.002 ) on generic E. coli concentrations in feces collected before shipment to slaughter. Main effect means were 5.57, 4.75, 5.00 and 4.08 log10 cfu/g for animals fed an experimental chlorate product at 0, 0.01% in last meal, 0.01% for last 5 d and 0.05% of body weight in last meal, respectively. A main effect of feed treatment was observed ( P = 0.041 ) on generic E. coli concentrations in feces collected at slaughter (means for the respective treatments were 4.92, 3.57, 3.98 and 3.20 log10 cfu/g) as well as on numbers of generic E. coli recovered ( P = 0.034 ) from hide swabs collected at the rump (means for the respective treatments were 4.86, 3.92, 3.87 and 4.06 log10 cfu/swab). A main effect of water treatment was observed ( P 0.016 ) on generic E. coli concentrations in rumen contents (3.44 vs. 2.72 cfu log10 cfu/g for animals administered 0 or 2500 ppm active chlorate ion, respectively). Logistic regression analysis revealed a main effect of feed treatment ( P 0.001 ) on the incidence of E. coli O157:H7 recovered from feces collected at slaughter (75%, 33%, 20% and 25% for animals fed an experimental chlorate product at 0%, 0.01% in last meal, 0.01% for last 5 d and 0.05% of body weight in last meal, respectively). Animals exhibited no symptoms of chlorate toxicity and negative effects on feed or water intake or animal performance were not observed.

The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (Por = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (Por = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (Por = 0.05), but not progesterone (Por = 0.05) Progesterone in culture media treated with RU-486 increased (Por = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (Por = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (Por = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (Por = 0.05). PGF2alpha was increased (Por = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (Por = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.

We conducted several experiments to better understand the relationship between brown adipose tissue (BAT) metabolism and thermogenesis. In Exp. 1, we examined perirenal (brown) and sternum s.c. adipose tissue in 14 Wagyu x Angus neonates infused with norepinephrine (NE). Perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum s.c. adipocytes contained a few, small mitochondria, with poorly developed cristae. Lipogenesis from acetate was high in BAT but barely detectable in sternum s.c. adipose tissue. In Exp. 2, we compared perirenal and tailhead adipose tissues between NE-infused Angus (n = 6) and Brahman (n = 7) newborn calves. Brahman BAT contained two-to-three times as many total beta-receptors as Angus BAT. The mitochondrial UCP1:28S rRNA ratio was greater in Brahman BAT than in BAT from Angus calves. Lipogenesis from acetate and glucose again was high, but lipogenesis from palmitate was barely detectable. Tail-head s.c. adipose tissue from both breed types contained adipocytes with distinct brown adipocyte morphology. In Exp. 3, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types, whereas the UCP1 gene expression tripled during gestation in both breed types. At birth, palmitate esterification was twice as high in Angus than in Brahman BAT and was at least 100-fold higher than in BAT from NE-infused calves from Exp. 2. Uncoupling protein-1 mRNA was readily detectable in tailhead s.c. adipose tissue in all fetal samples. In Exp. 4, male Brahman and Angus calves (n = 5 to 7 per group) were assigned to 1) newborn treatment (15 h of age), 2) 48 h of warm exposure (22 degrees C) starting at 15 h of age, or 3) 48 h of cold exposure (4 degrees C) starting at 15 h of age. Brahman BAT adipocytes shrank with cold exposure, whereas Angus BAT adipocytes did not. Similarly, BAT from neonatal lambs (Exp. 5; n = 6 per group) was depleted of lipid in response to cold exposure, although UCP1 gene expression persisted. In Exp. 4, NE stimulated lipogenesis from palmitate in BAT incubated in vitro. Lipogenesis from palmitate was higher in Angus than in Brahman BAT, and increased with both warm and cold exposure. These studies suggest that BAT from Brahman calves may be exhausted of lipid shortly after birth during times of cold exposure.

Brahman calves experience greater neonatal mortality than Angus calves if cold-stressed. To establish a developmental basis for this, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Overall fetal BW tended (P = 0.08) to be greater for Angus than for Brahman fetuses. There was no difference between breed types in total brown adipose tissue (BAT) mass or grams of BAT/kg BW. Brown adipocyte density decreased 56%, whereas lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types. Glycerolipid synthesis from palmitate declined by 85% during the last trimester but still contributed 98% to total lipid synthesis at birth. The fetal age x breed interaction was significant for lipogenesis from glucose (P = 0.05) and palmitate (P = 0.005); rates were higher at 96 d before birth in Brahman BAT but declined to similar rates by birth. Uncoupling protein-1 (UCP1) mRNA tripled during gestation in both breed types (P = 0.002), whereas mitochondrial cross-sectional area did not change (P = 0.14) during gestation. Neither the breed nor the age x breed effect was significant (P > or = 0.24) for UCP1 mRNA concentration or mitochondrial cross-sectional area. In both breed types, a marked decrease in BAT UCP1 mRNA between 24 and 14 d prepartum was associated with a similar reduction in lipogenesis from palmitate and a noticeable change in BAT mitochondrial morphology, as the mitochondria became more elongated and the cristae became more elaborate. Uncoupling protein-1 mRNA initially was elevated in Angus tailhead s.c. adipose tissue, but was barely detectable by birth, and tended to be greater overall (P = 0.09) in Angus than in Brahman BAT. If uncoupling protein activity in s.c. adipose tissue persists after birth, then s.c. adipose tissue may contribute more to thermogenesis in Angus newborn calves than in Brahman calves. In contrast, we did not observe differences in ontogenic development of perirenal BAT that could explain the documented differences in thermogenic capacity between Angus and Brahman newborn calves.

We examined the effect of prepartum protein restriction on thermogenesis and several aspects of perirenal (brown) adipose tissue (BAT) in newborn calves. Lipid synthesis and morphology also were compared between BAT and sternum (white) adipose tissue. During the last 140 d of gestation, heifers were fed isocaloric diets containing adequate (10.4%) or restricted (average of 6.8%, dry matter basis) levels of protein. Body condition scores and weight gain during gestation were significantly lower in heifers fed the restricted-protein diet. However, newborn calf birth weight, calf BAT weight and composition, and calf thermoneutral metabolic rates were not affected by prepartum protein restriction. Similarly, visceral organ weights, except for lung plus trachea, were not affected (P > 0.10) by prepartum protein treatment. Peak metabolic rates were not affected (P > 0.10) by prepartum protein treatment and on average were twice the thermoneutral metabolic rates. Consistent with this, BAT of calves from heifers fed adequate- or restricted-protein diets did not differ in lipid synthesis, cellularity, or uncoupling protein mRNA:28S rRNA ratios. Although both perirenal and sternum adipocytes were mostly unilocular, perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum adipocytes contained a small number of mitochondria with poorly developed cristae. Fatty acid biosynthesis from acetate was high in BAT (55-57 nmol acetate incorporated. 100 mg -l . h -l ) but barely detectable in sternum adipose tissue. Conversely, fatty acid biosynthesis from glucose was 80-110% higher in sternum adipose tissue than in BAT (4.5 vs 2.1-2.5 nmol glucose incorporated 100 mg -l . h -l ). Thus maternal protein restriction severely affected heifers but had no effect on neonatal calf thermogenesis or BAT function.

The objectives of this study were to determine if residual feed intake (RFI) classification of beef heifers affected efficiency of forage utilization, body composition, feeding behavior, heart rate, and physical activity of pregnant females. Residual feed intake was measured in growing Bonsmara heifers for 2 yr (n=62 and 53/yr), and heifers with the lowest (n=12/yr) and highest (n=12/yr) RFI were retained for breeding. Of the 48 heifers identified as having divergent RFI, 19 second-parity and 23 first-parity females were used in the subsequent pregnant-female trial. Pregnant females were fed a chopped hay diet (ME=2.11 Mcal kg(-1) DM) in separate pens equipped with GrowSafe bunks to measure individual intake and feeding behavior. Body weights were measured at 7-d intervals and BCS and ultrasound measurements of 12th-rib fat depth, rump fat depth, and LM area obtained on d 0 and 77. Heart rate and physical activity were measured for 7 consecutive d. First-parity females had lower (P

Residual feed intake (RFI) quantifies inter-animal variances in dry matter intake (DMI) independent of variation in body size and productivity (e.g. growth, milk). In beef cattle, Herd and Arthur (2009) estimated that approximately one-third of the biological variation in RFI was due to inter-animal differences in digestion, heat increment, body composition, and activity, with the remaining variation associated with energy expenditure of metabolic processes. Given that RFI is independent of BW and level of production, it is an ideal trait for discovery of genomic regions (Rolf et al., 2011) and functional genes (Chen et al., 2011) associated with efficiency of feed utilization. Some variation in RFI may be caused by individual differences in immune system function. The immune system is an energetically expensive system. A previous study showed that metabolic heat production and oxygen consumption increased 20-30% in mice that were immunized with a relatively benign antigen (Demas et al., 1997). The objective of this work was to examine whether the genes associated with the immune system were differentially expressed by beef cattle with divergent RFI phenotypes.

Eighteen commercial Angus cross-bred feedlot steers of similar hip height and live weight were randomly assigned to one of three dietary treatment groups: corn-, corn/barley, or barleybased diets ( n = 6 per treatment). Steers were fed for 102–103 days on their respective diets prior to slaughter. Live animal performance traits, carcass characteristics, total lipid and descriptive flavor and descriptive palatability attributes of beef strip loin steaks were determined. End live weight ( P = 0.88) did not differ between dietary treatments. Beef carcasses from steers fed corn-, barley-, and corn/barley-based diets did not differ in hot carcass weight ( P = 0.18), ribeye area ( P = 0.21), kidney, pelvic and heart fat (KPH) ( P = 0.35), and yield grade ( P = 0.14). However, adjusted preliminary yield grade was higher ( P = 0.03) for carcasses from steers fed corn/barley-based diets than carcasses from steers fed barley as the dietary energy source. These data suggest that carcasses from steers fed barley-based diets were lower in external fat. Quality grade characteristics were not different in beef carcasses from steers fed either corn-, barley-, or a corn/barley-based diet. Cook time ( P = 0.37), cooking loss ( P = 0.83), descriptive meat palatability attributes ( P > 0.27), Warner-Bratzler shear force ( P = 0.25), and descriptive sensory flavor attributes ( P ≥ 0.17) did not differ for steaks from steers fed the three diets prior to slaughter. The Japanese have claimed that feeding cattle barley-based high energy diets result in beef with different flavor than when cattle are fed high-energy corn-based diets. These results indicated that the eating quality, tenderness and flavor attributes of beef steaks were not influenced by the dietary grain source fed to young steers in this study prior to slaughter.

During the fetal to neonatal transition, the newborn calf encounters severe thermolysis due to an abrupt change in thermal environment that is compounded by evaporation of fetal fluids and severe weather conditions. Maintenance of homeothermy during the neonatal period necessitates an acute and sustained thermogenic response by the newborn calf. It is now widely accepted that this thermogenic response is derived from both shivering thermogenesis in muscle tissue and nonshivering thermogenesis in brown adipose tissue (BAT). It is critical that newborn calves possess functional BAT during the neonatal period. This article focuses on the pre- and postnatal factors that influence nonshivering thermogenesis of BAT in the neonatal calf.

Pathogenic bacteria attached to the hide or shed in the feces of cattle at slaughter can contaminate carcasses intended to be processed for human consumption. Therefore, new pre-harvest interventions are needed to prevent the carriage and excretion of foodborne pathogens in cattle presented to the processing plant. The objectives of this study were to examine the antimicrobial effects of hydrolysable tannin-rich chestnut and condensed tannin-rich mimosa extracts on bacterial indicators of foodborne pathogens when applied as a hide-intervention and as a feed additive to feedlot cattle. Water (control) or solutions (3 % wt/vol) of chestnut- and mimosa-extract treatments were sprayed (25 mL) at the left costal side of each animal to a 1000 cm² area, divided in four equal quadrants. Hide-swabs samples obtained at pre-, 2-min, 8-h, and 24-h post-spray application were cultured to enumerate Escherichia coli/total coliforms and total aerobic plate counts. In a second experiment, diets supplemented without (controls) or with (1.5 % of diet dry matter) chestnut- or mimosa-extracts were fed during a 42-day experimental feeding period. Weekly fecal samples starting on day 0, and rumen fluid obtained on days 0, 7, 21 or 42 were cultured to enumerate E.coli/total coliforms and Campylobacter. Tannin spray application showed no effect of treatment or post-application-time (P > 0.05) on measured bacterial populations, averaging 1.7/1.8, 1.5/1.6 and 1.5/1.7 (log₁₀CFU/cm²) for E. coli/total coliforms, and 4.0, 3.4 and 4.2 (log₁₀CFU/cm²) in total aerobes for control, chestnut and mimosa treatments, respectively. Mean (± SEM) ruminal E. coli and total coliform concentrations (log(10) CFU/mL) were reduced (P < 0.01) in steers fed chestnut-tannins (3.6 and 3.8 ± 0.1) in comparison with the controls (4.1 and 4.2 ± 0.1). Fecal E. coli concentrations were affected by treatment (P< 0.01), showing the highest values (log₁₀ CFU/g) in fecal contents from mimosa-fed steers compared to controls (5.9 versus 5.6 ± 0.1 SEM, respectively). Total coliforms (log CFU/g) showed the highest values (P < 0.01) in feces from chestnut- and mimosa-fed steers (6.0 and 6.1 ± 0.1 respectively) in comparison with controls (5.7 ± 0.1). Fecal Campylobacter concentrations (log₁₀CFU/g) were affected by treatment (P < 0.05), day (P < 0.001) and their interaction (P < 0.01) with the controls having lower concentrations than chestnut- and mimosa-fed steers (0.4, 1.0, and 0.8 ± 0.3, respectively). It was concluded that under our research conditions, tannins were not effective in decreasing measured bacterial populations on beef cattle hides. Additionally, chestnut tannin reduced E. coli and total coliforms within the rumen but the antimicrobial effect was not maintained in the lower gastrointestinal tract. Further research is necessary to elucidate the possible antimicrobial effects of tannins at site-specific locations of the gastrointestinal tract in beef cattle fed high-grain and high-forage diets.

Seventy-two crossbred wether lambs (average initial weight, 25.1 kg) were used to determine the interaction between zeranol treatment and two dietary levels of Ca and P (.8 and .6% vs .4 and .3% Ca and P, respectively) in a 2 x 2 factorial arrangement on performance, carcass and bone characteristics, and serum concentrations of parathyroid hormone (PTH) and Ca. Lambs were implanted on d 0 and 56 with 12 mg of zeranol. Lambs had ad libitum access to feed for 105 d. On d 99, blood samples were collected. Implanted lambs had 12% greater (P less than .01) daily feed intake, 26% greater (P less than .10) ADG, and a 12% improvement in (P less than .10) feed efficiency compared with nonimplanted lambs. Zeranol-treated lambs had increased (P less than .05) bone cortical area, breaking load, and width of the metacarpal compared with nonimplanted lambs. Lambs fed the .8% Ca and .6% P diet had a higher (P less than .05) percentage of bone ash than lambs fed the .4% Ca and .3% P diet. However, there were no differences (P greater than .05) in the percentage of Ca, P, Mg, or Zn in metacarpal bones due either to higher dietary Ca and P or to implant treatments. Serum concentration of PTH was greater (P less than .10) in lambs fed .8% Ca and .6% P than in those receiving .4% Ca and .3% P. Serum concentrations of PTH and Ca pooled across treatments were greater (P less than .05) before feeding than at 1 h after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

We examined the response of selected animal performance, endocrine, immune, and metabolic factors from 13 steers (254+/-6.1 kg) with and without a lone star (Amblyomma americanum) tick burden during progressive days of the tick feeding cycle. Steers were randomly assigned to either non-treated controls or treated with 300 adult pair of A. americanum per animal. Animals were weighed and blood sampled on days -7, 0, 10, 14, 21, 28, and 35 relative to tick treatment. Tick treatment did not affect (P0.1) animal performance. Experimental day did (P0.05) affect body weight gain and dry matter intake. Tick treatment did not affect (P0.1) metabolic indicators. Experimental day affected (P0.05) IGF1 and lactate, tended to affect cortisol (P0.07), but did not affect (P0.1) glucose concentrations. Tick treatment did not significantly (P0.1) affect growth hormone receptor (GHR) mRNA in liver, but liver tissue from treated animals had numerically lower GHR mRNA than did tissue from control animals. Day had a significant (P0.05) effect on liver GHR mRNA. There was a significant treatment by day interaction (P0.05) for liver IGF1 gene expression, as IGF1 mRNA was reduced in tick-treated cattle versus control cattle on day 35. Overall, liver IGF1 gene expression was lower (P0.05) in tick than in control animals while there was no effect (P0.1) due to day. Within the tick-treated group, correlations were found between quantitative female tick feeding characteristics and host metabolic indicators. Feeding by adult female lone star ticks did cause acute stress in growing beef steers on a moderate plane of nutrition as indicated by some physiologic indicators. In particular there may be longer term effects on the somatotrophic axis in the liver which could affect subsequent (i.e. feedlot) performance. It is not known how these observed effects would be manifest under a lower plane of nutrition, as is common and may become more so within the current native range of A. americanum. Other acute effects due to tick feeding may have been masked by the effects of handling and invasive sampling. Non-invasive experimental procedures are called for in order to study the effects of a stressor such as arthropod infestation on grazing animals. Future research efforts will be aimed at non-invasively elucidating the effects of tick stress on grazing animals under various nutritional environments.

Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between actual feed intake and expected feed intake required for maintenance and production. The objective of this study was to determine the relationship between RFI, feeding behavior, and other performance traits in growing heifers. Individual DMI was measured in Brangus heifers (n = 115) fed a roughage-based diet (ME = 2.0 Mcal/kg) for 70 d using Calan-gate feeders. Residual feed intake was computed as the residuals from linear regression of DMI on mid-test BW(0.75) and ADG. Heifers with the greatest (least efficient, n = 18) and least (most efficient, n = 18) RFI were identified for quantification of feeding behavior traits. Continuous video recordings were obtained for all heifers during d 28 through d 56 of the 70-d feeding trial. Video data of 2 replications of four 24-h periods, 2 wk apart, were analyzed for the focal heifers. A head-down feeding event was defined as a heifer positioned in the feeder with her head lowered. A meal included all head-down feeding events that were separated by less than 300 s. The mean RFI for the high- and low-RFI heifers were 1.00 and -1.03 +/- 0.03 kg/d, respectively. High-RFI heifers consumed 21.9% more (P < 0.0001) DM but had similar BW and ADG compared with low-RFI heifers. The high-RFI heifers spent less time in head-down feeding events per day (P < 0.0001; 124 vs. 152 +/- 4.3 min/d), consumed DM at a faster rate (99.6 vs. 62.8 +/- 3.3 g/min), and ate more often per day (119.1 vs. 90.5 +/- 3.9 head-down feeding events/d) compared with the low-RFI heifers; however, meal duration and frequency were not related to RFI. We conclude that feeding behavior related to head-down feeding events may be more useful as an indicator of RFI than the number of meal events.

Nitroethane is a potent inhibitor of ruminal CH 4 production, a digestive inefficiency resulting in the loss of 2-15% of a ruminant's gross energy intake and an important emission source of this greenhouse gas. To assess the effect of nitroethane on methanogenesis and characterize ruminal adaptation observed with low treatment doses to this inhibitor, ruminal microbes were cultured in vitro with supplements of water (controls), 4.5 and 9 mM nitroethane, and 0.09 mM monensin, with or without 9 mM nitroethane. All treatments decreased CH 4 production78% compared to controls; however, differential effects of treatments were observed on CO 2, butyrate isobutyrate, and valerate production. Treatments did not affect H 2 accumulation or acetate and propionate production. Most probable numbers of nitrometabolizing bacteria were increased with 4.5 and 9 mM nitroethane compared to numbers recovered from controls or monensin-containing treatments, which may explain ruminal adaptation to lower nitroethane treatments.

The effects of several methane-inhibitors on rumen fermentation were compared during three 24 h consecutive batch cultures of ruminal microbes in the presence of nonlimiting amounts of hydrogen. After the initial incubation series, methane production was reduced greater than 92% from that of non-treated controls (25.8 ± 8.1 μmol ml −1 incubation fluid) in cultures treated with nitroethane, sodium laurate, Lauricidin ® or a finely-ground product of the marine algae, Chaetoceros (added at 1, 5, 5 and 10 mg ml −1 , respectively) but not in cultures treated with sodium nitrate (1 mg m1 −1 ). Methane production during two successive incubations was reduced greater than 98% from controls (22.5 ± 3.2 and 23.5 ± 7.9 μmol ml −1 , respectively) by all treatments. Reductions in amounts of volatile fatty acids and ammonia produced and amounts of hexose fermented, when observed, were most severe in sodium laurate-treated cultures. These results demonstrate that all tested compounds inhibited ruminal methane production in our in vitro system but their effects on fermentation differed.

Relationships of temperament evaluated at different production stages with growth, carcass characteristics and beef tenderness were determined in Bonsmara crossbred steers managed under commercial managent. Temperament was evaluated at weaning and at initiation of the finishing phase. Steers from a Roswell, NM ranch (n=156) and a Cline, TX ranch (n=21) were stratified at fall weaning by weight and source and randomly allotted to winter ryegrass at Uvalde or Overton, TX followed by feeding in a commercial feedlot near Batesville, TX. Cattle were observed for temperament (escape velocity, EV, m/s; pen and chute temperament score, PTS and CTS) at weaning and upon entry to the feedlot. Cattle were harvested at approximately 7 mm 12th rib fat. Carcass data was taken approximately 36 hrs post-mortem and 2.5cm thick steaks were removed from the 13th rib for Warner-Bratzler shear force (WBS) determination. The only measures of temperament significantly related to performance were EV and PTS. Weaning EV appeared to be more related to feedlot ADG (r=-0.26, P0.003), ribeye area (r=-0.37, P0.0008), yield grade (r=0.29, P0.01) and WBS, r=0.27, P0.005) than did the later measures of temperament. However, in-feedlot EV was associated with feedlot weights (r=-0.28, P0.0004). Results of this research suggest temperament, particularly at weaning, is related to feedlot performance, carcass merit, and beef tenderness at a low to moderate level and evaluation of this trait may be a helpful management tool.

Background: The use of stable isotopes has provided valuable insights into iron absorption in humans, but the data have been limited to nonheme iron. Objective: Our objectives were to produce heme iron enriched in 58 Fe and to use it to study the absorption of heme iron and the effect of iron and zinc intakes on heme-iron absorption in children. Design: Labeled bovine heme was produced in a bovine model. Forty-eight children were randomly assigned to consume identical meals containing 1 of 3 doses of labeled heme iron (2,4, or 8 mg as hemoglobin) and 1 of 2 doses of inorganic zinc (1 or 9 mg); successful measurements of iron absorption, zinc absorption, or both were made in 40 of these subjects. We hypothesized that fractional heme-iron absorption would decrease as heme-iron intake increased and that higher zinc intakes would decrease heme-iron absorption. Results: 58 Fe heme was produced with an enrichment (mass/mass) of 9.5%. Fractional iron absorption in children was significantly affected by the intake of heme iron (P = 0.0013) and of zinc (P = 0.0375), but, contrary to expectations, heme-iron absorption was higher at higher zinc intakes. Absolute heme-iron absorption was higher in the group with higher zinc intakes, but only for those with the lowest heme-iron intake (2 mg; P = 0.0147). Although fractional zinc absorption decreased as zinc intake increased (P = 0.031), absolute zinc absorption continued to increase across the intake range studied (P = 0.018). Conclusions: Heme iron intrinsically labeled with 58 Fe can be produced at sufficient enrichments for use in human studies. In children, heme iron and zinc absorption decrease as the dose of each mineral increases. Heme iron did not inhibit zinc absorption. At lower heme intakes, zinc intakes may increase heme-iron absorption.

Strategies are sought to reduce economic and environmental costs associated with ruminant methane emissions. The effect of oral nitroethane or 2-nitropropanol administration on ruminal methane-producing activity and volatile fatty acid production was evaluated in mature ewes. Daily administration of 24 and 72 mg nitroethane/kg body weight reduced (P < 0.05) methane-producing activity by as much as 45% and 69% respectively, when compared to control animals given no nitroethane. A daily dose of 120 mg 2-nitropropanol/kg body weight was needed to reduce (P < 0.05) methane-producing activity by 37% from that of untreated control animals. Reductions in methane-producing activity may have been diminished by the last day (day 5) of treatment, presumably due to ruminal adaptation. Oral administration of nitroethane or 2-nitropropanol had little or no effect on accumulations or molar proportions of volatile fatty acids in ruminal contents collected from the sheep. These results demonstrate that nitroethane was superior to 2-nitropropanol as a methane inhibitor and that both nitrocompounds reduced ruminal methanogenesis in vivo without redirecting the flow of reductant generated during fermentation to propionate and butyrate.

Publisher Summary This chapter focuses on brown adipose tissue (BAT) in lambs and calves. Distinctive brown adipocytes do not appear to be present in porcine adipose tissue. Several aspects of BAT development and response to environmental stimuli are described in the chapter. The metabolism of BAT resembles from mature ruminant white adipose tissue, in that acetate is the primary precursor for lipogenesis. There is a precipitous decline in rates of de novo lipogenesis during the last trimester, indicating that the contribution of fatty acid biosynthesis to lipid filling is important earlier in fetal development. The mixture of brown and white adipocytes in subcutaneous adipose tissues from newborn calves suggests that brown adipocytes may involute into white adipocytes in this species. In rodent species, brown and white adipocytes differentiate and develop independently. Brown adipose tissue from sheep and cattle rapidly dedifferentiates and/or is lost through apoptosis early postnatally. In Wagyu × Angus crossbred calves; brown adipose tissue function is remarkably refractory to profound reductions in dietary protein intake in dams, indicating the high priority animals place in ensuring adequate thermogenic capacity in their newborn.

Effects of feeding sodium chlorate on carcass quality, tenderness and color stability were evaluated. Heifers (n=64) were fed chlorate at either 0.01% or 0.05% of body weight (BW) in the last feeding or 0.01% for the last 5d before harvest, while control cattle received no chlorate. During the 12h period between feed withdrawal and transport to the harvest facility, the cattle were provided water containing either no sodium chlorate or sodium chlorate (approximately 30mM). Feed treatments at 0.01% of BW produced higher marbling scores than feeding 0.01% of BW for 5d. However, neither of these treatments produced marbling scores that were different from non-treated controls. Water supplementation increased tenderness in cattle fed 0.01% of BW for 5d, but decreased tenderness in cattle fed 0.05% of BW at the last feeding. Although tenderness differences existed, it is not clear whether or not they were caused by the feed or water treatments or by pre-existing variation in the cattle. Neither feed nor water supplementation affected color stability. These data suggest that chlorate preparations could be used to reduce pathogens without adversely impacting meat quality or display life. However, further research is needed to further substantiate these findings.

The objective of this study was to compare adipocyte morphology and lipogenesis between breed types (Angus vs Brahman) in brown adipose tissue (BAT) and white adipose tissue (WAT) from newborn calves. The Brahman calves (n = 7) were born during the fall season, whereas the Angus calves were born in fall (n = 6) or the following spring (n = 4). At parturition, Brahman cows were lighter than fall Angus cows, but were heavier than spring Angus cows (P < .05). Birth weights and perirenal BAT weights were greater in spring-born, but not in fall-born Angus calves, than in Brahman calves (P < .05). Fall-born Angus BAT contained 63% more (P < .05) adipocytes/100 mg tissue and contained a greater proportion (P < .05) of adipocytes with mean diameters of 40 to 50 microm, and fewer adipocytes with diameters of 60 microm or greater, than Brahman BAT. Brahman BAT contained two-to-three times as many beta-receptors as Angus BAT (P < .05), although the dissociation constant (Kd) was not different between breed types. Mitochondria in Brahman BAT were primarily spherical, whereas Angus BAT mitochondria were elongated, and mitochondrial cross-sectional area tended (P = .08) to be greater in Brahman BAT than in Angus BAT. The mitochondrial uncoupling protein (UCP) mRNA concentration (per 10(6) cells) was greater in Brahman BAT than in BAT from fall-born Angus calves. Lipogenesis from acetate was greater in Angus BAT than in Brahman BAT (P < .05), and glucose and palmitate contributed a greater proportion of carbon to lipogenesis in Brahman BAT than in Angus BAT. These differences in lipogenesis between breed types were not observed in s.c. WAT. The WAT from both breed types contained adipocytes with distinct brown adipocyte morphology, suggesting an involution of BAT to WAT in utero. We conclude that differences in UCP gene expression cannot cause the greater peak thermogenesis of Angus calves; however, differences between breed types in lipid metabolism and(or) mitochondrial morphology may contribute to this phenomenon.

Angus × Holstein heifers (initial age and BW: 6.0 ± .4 mo; 159 ± 12 kg) were assigned to one of four treatments (n = 10) in a 2 × 2 factorial arrangement to examine the effects of bovine somatotropin (bST) or vehicle treatment and continu- ous ( CG) or intermittent growth (IG) pattern treat- ment on mammogenesis. Subcutaneous injections of bST (500 mg) or vehicle were administered at 14-d intervals. The CG heifers were limit-fed a diet to gain .8 kg/d throughout the experiment, whereas IG heifers underwent two successive growth restriction- compensation phases with each phase consisting of a 3-mo growth restriction period (.25 kg/d) followed by a growth compensation period. All heifers were individually fed during the experiment and slaugh- tered when average treatment BW reached 390 kg. Mammary gland development was measured by dis- section, chemical analysis, and computed tomography scanning. Overall ADG were increased ( P < .001) 20% by bST treatment of CG heifers, although ADG of IG- vehicle and IG-bST heifers were similar to ADG of CG- vehicle heifers. Dissectable extraparenchymal tissue (EPT) mass was reduced 23% ( P < .05) and 36% (P < .001) by IG pattern and bST treatments, respectively, although the bST effect on dissectable EPT tended ( P = .08) to be greater in CG than in IG heifers. Fat-free parenchymal tissue (PT) mass ( P = .11) and PT volume ( P = .08) tended to be greater in IG than in CG heifers. Fat-free PT was 60% greater ( P = .01) and PT volume onefold higher ( P = .01) in bST than in vehicle heifers. The bST and IG pattern treatments increased the proportional weight of fat-free PT mass, although the effect of bST was greater than IG pattern treatment. There was no evidence to suggest that the two treatments were additive in affecting mammogen- esis.

Forty crossbred wethers (average weight 30 kg) were implanted with zeranol (12 mg) at 30-d intervals and fed at two levels of intake in a 2 x 2 factorial arrangement of treatments to determine performance, carcass and bone characteristics, blood metabolites, and hormones. Restricted lambs were fed to gain one-half the BW gained by lambs with ad libitum feed access. Lambs with ad libitum and restricted access to feed were slaughtered after 98 and 154 d, respectively. Zeranol increased ADG ( P =.047 ; 20%), gain to feed ( P =.023 ; 17%), metacarpal length (P =.004 ; 6%) and weight (P =.013 ; 13%), and tended to increase carcass crude protein gain (P = .106 ; 63%) while reducing kidney pelvic fat (P =.001 ; 33%) and dressing percentage (P =.038 ; 3%). Restricted feed intake increased the percentage of carcass ash and metacarpal length and weight by 27% (P =.048), 5% (P =.006), and 10% (P =.045), respectively, while reducing quality grade scores ( P = .022 ; 5%), gain to feed (P =.001 ; 49%), longissimus muscle area ( P =.001 ; 28%), the percentage of kidney pelvic fat (P =.033 ; 13%), and daily fat gain (P = .001 ; 54%). Zeranol increased pituitary weight (P = .001 ; 166%), plasma glucose (P =.036 ; 13%), mean serum growth hormone (GH ; P =.011 ; 52%), baseline GH (P =.048 ; 34%), GH pulse amplitude (P =.003 ; 59%), and IGF-I (P =.001 ; 53%) concentrations. The results indicate that continuous administration of zeranol from 60 d of age to slaughter increases GH release, which directs nutrient utilization such that a carcass with more desirable lean and fat deposition patterns is obtained when nutrient availability is adequate.

Heat production was measured in newborn Angus-, Brahman-, and Tuli-sired calves born to Angus (n = 20) and Brahman (n = 26) dams, before (thermoneutral metabolic rate, TMR) and after norepinephrine (NE) infusion (peak metabolic rate, PMR), to assess genotypic effects on nonshivering thermogenesis in brown adipose tissue. Calves were fed pooled colostrum, fitted with jugular catheters, and placed in a temperature-controlled (37 degrees C) water immersion system. Heat production, determined by indirect calorimetry, and tympanic temperature were measured continuously in calves from approximately 3 to 6 h of age. Blood samples were collected at birth and at 0, 5, 20, 40, 60, 80, 100, and 120 min relative to NE infusion (35 micrograms.min-1.kg BW-1 for 4 min), and plasma was analyzed for metabolites (glucose, NEFA, and urea nitrogen [PUN]) and hormones (cortisol, triiodothyronine [T3] and thyroxine [T4]). Weight-specific TMR (cal.min-1.kg-1) was not affected by breed of sire or dam, although weight-specific PMR (cal.min-1.kg-1) was lower (P.01) in Brahman-sired calves than in Angus- or Tuli-sired calves and was lower (P.001) in calves born to Brahman rather than Angus dams. The reduction in weight-specific PMR due to the maternal Brahman influence was sire-breed dependent, and the reduction was largest (P.01) for Tuli-sired (34.3%), intermediate (P.05) for Brahman-sired (15.1%), and lowest (P.25) for Angus-sired calves (4.1%). The PMR:TMR ratio was 1.80 and 2.21 +/- .06 in calves born to Brahman and Angus dams, respectively. Peak tympanic temperature was .6 degree C lower (P.01) in calves born to Brahman rather than Angus dams. At birth, plasma NEFA concentrations were higher (P.001) and glucose tended (P = .13) to be higher in calves born to Brahman rather than Angus dams. Cortisol, T3, and T4 concentrations at birth were higher in calves born to Brahman dams than in those born to Angus dams. These results suggest that calves born to Brahman dams may have less thermogenically active brown adipose tissue than calves born to Angus dams, which may contribute to the relative cold intolerance of calves with Bos indicus inheritance.

Purebred Bos indicus calves are documented to have lower survival rates than Bos taurus calves. Thus, this study was designed to investigate the possibility that this decreased survival rate may be attributed to dam colostral immunoglobulin (Ig) concentrations and subsequent calf serum Ig concentrations. The specific objective was to determine the effect of breed type of calf on colostrum production, immunoglobulin concentrations in colostrum and calf serum, and availability and absorption efficiency of Ig. Brahman (B) and Angus (A) cattle were reciprocally mated to produce calves of the following types: A x A (n = 8), A x B (n = 9), B x B (n = 11), and B x A (n = 11). At birth, calves were separated from their dams and a blood sample was collected before feeding pooled colostrum (30 mL/kg birth weight) at 1 and 6 h of age. From 6 to 12 h of age, each calf was placed in a box that allowed interaction with the dam but prevented suckling. At 12 h of age, each calf was fed its dam's colostrum and placed with the dam. Additional blood samples were collected at 12, 24, and 48 h after birth. Serum and colostrum samples were analyzed for IgG, IgG1, IgG2, IgM, and IgA using single radial immunodiffusion (RID) assay techniques. The cows were hand-milked after induction of milk letdown with oxytocin at 1 and 12 h after calving. Colostrum volume was recorded, and samples were collected. Brahman cows produced more (P < .001) colostrum at 1 and 12 h than A cows. Total Ig concentrations were obtained by summing IgG, IgG1, IgG2, IgM, and IgA concentrations. Total Ig (P < .02), IgG (P < .005), and IgA (P < .01) concentrations in colostrum were greater in cows producing crossbred calves. Total Ig (P < .006), IgG (P < .02), IgG1 (P < .004), and IgG2 (P < .02) available in colostrum were affected by B x B and A x B breed types of calf. Brahman cows had more Ig available at 1 and 12 h than A cows due to increased production of colostrum. Breed type influenced colostral Ig in cattle. Serum concentrations of total Ig, IgG, IgG1, IgG2, IgM, and IgA in the calf and efficiency of absorption at 6 and 12 h were not affected by breed type, sex of calf, or any interaction.

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)