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Twenty-eight Angus steers (289 kg) were finished on a high-concentrate diet (85% concentrate:15% roughage; CONC), or endophyte-free tall fescue pastures with corn grain supplement (0.52% of BW; PC), corn oil plus soybean hull supplement (0.10% of BW corn oil plus 0.45% of BW soybean hulls; PO), or no supplement (pasture only; PA). Subcutaneous adipose tissues were processed for total cellular RNA extraction and fatty acid composition by GLC. Relative expression of genes involved in lipogenesis [fatty acid synthase (FASN), acetyl-CoA carboxylase, lipoprotein lipase, stearoyl-GoA desaturase (SCD)] and activators of transcription [(peroxisome proliferator-activated receptor-γ), C/EBPα, sterol regulatory binding protein-1, signal trallsducer and activator of transcription-5, and Spot-14] was determined by real-time quantitative PCR. Housekeeping gene (glyceraldehyde 3-phosphate dehydrogenase and β-actin) expression was used in analysis to normalize expression data. Total fatty acid content was greatest (P < 0.001) for CONC and least (P < 0.001) for PA. Supplementation of grazing cattle increased (P < 0.001) total fatty acid content compared with PA, but concentrations were less (P < 0.001) than for CONC. Myristic and palmitic acid contents were greater (P < 0.001) for CONG than for PO and PC, which were greater (P < 0.001) than for PA. Stearic acid content was greater (P < 0.01) for PO than for GONG, PC, and PA. Finishing on GONG increased (P < 0.001) total MUFA content by 68% compared with PA. Corn grain supplementation increased (P < 0.001) MUFA content compared with PA; in contrast, MUFA content did not differ (P> 0.05) between PO and PA. Corn oil supplementation increased (P < 0.001) trans-11 vaccenic acid content in subcutaneous fat by 1.2-, 1.7- and 5.6-fold relative to PA, PC, and CONC, respectively. Concentrations of the cis-9, trans-11 CLA isomer were 54, 58, and 208% greater (P < 0.01) for PO than for PA, PC, and CONC, respectively. Corn grain supplementation to grazing steers did not alter (P > 0.05) the cis-9, trans-11 CLA isomer compared with PA. Oil supplementation increased (P < 0.001) linoleic acid (C18:2) content by 56, 98 and 262% compared with CONC, PC, and PA, respectively. Relative mRNA expression of SCD was upregulated (P < 0.001) by 46-, 18- and 7-fold, respectively, for CONC, PC, and PO compared with PA. Relative FASN mRNA expression was also upregulated (P = 0.004) by 9- and 5-fold, respectively, for CONC and PC compared with PA. Grain feeding, either on CONC or supplemented on pasture, upregulated FASN and SCD mRNA to increase MUFA and de novo fatty acids in subcutaneous adipose tissue. Upregulation of SCD with grain feeding and reduced tissue CLA concentrations suggest that the decreased CLA concentrations were the result of limited substrate (trans-11 vaccenic acid) availability. [ABSTRACT FROM AUTHOR]

Twenty-eight Angus (289 ± 3.8 kg) steers were used in a completely randomized design to evaluate the effect of isocaloric supplementation of 2 different energy sources to steers rotationally grazing tall fescue pastures for 197 d in comparison to positive and negative controls. Steers were supplemented with either corn grain (0.52% BW on a DM basis; PC) or soybean hulls plus corn oil (0.45% BW on a DM basis + 0.10% BW on an as-fed basis; PO) using Calan gates for individual intake measurement. Negative, pasture only (PA), and positive, high-concentrate control diets (85% concentrate:15% roughage on DM basis; C) were also included in the study. Steers on PC, PO, and PA treatments were managed together under a rotational grazing system, whereas C steers were fed a high-concentrate diet for the final 113 d using Calan gates. Forage DM1 and apparent DM and NDF digestibility for the grazing treatments were evaluated using Cr2O5 and indigestible NDF as digesta markers. Energy supplementation decreased (P = 0.02) forage DM1 (% of BW) with respect to PA, but not (P = 0.58) total DM1. There were no differences (P = 0.53) among grazing treatments on apparent total DM digestibility. How- ever, NDF digestibility was less (P ≤ 0.05) in PC than in PO and PA; the latter 2 treatments did not differ (P > 0.05). Overall ADG was greater (P < 0.01) in supplemented, regardless of type, than in nonsupplemented grazing treatments. During the final 113 d, ADG was greater (P < 0.01) in C than in the grazing treatments. Overall supplement conversion did not differ (P = 0.73) between supplement types and was less (P = 0.006) than C. Carcass traits did not differ (P> 0.05) between energy sources. Dressing percentage and HCW were greater (P < 0.01) in supplemented cattle than in PA. Fat thickness and KPH percentage for PA were less (P <0.05) than for PO but did not differ (P> 0.14) from PC. Marbling score, LM area, and quality grade did not differ (P> 0.05) between grazing treatments. Hot carcass weight for C was heavier (P < 0.00 1) than for pastured cattle. Quality and yield grades of C carcasses were also greater (P < 0.001) than carcasses from pastured steers. Energy supplementation, regardless of source, to grazing steers increased ADG, dressing percentage, and carcass weight compared with PA steers; however, supplemented steers had less ADG, efficiency, dressing percentage, and carcass weight compared with high- concentrate finished steers. [ABSTRACT FROM AUTHOR]

Eighteen steers were used to evaluate the effect of supplemental corn oil level to steers grazing endophyte-free tall fescue on fatty acid composition of LM, stearoyl CoA desaturase (SCD) activity and expression as well as cellularity in s.c. adipose. Corn oil was supplemented (g/kg of BW) at 0 (none), 0.75 (medium), and 1.5 (high). Cottonseed hulls were used as a carrier for the corn oil and were supplemented according to pasture availability (0.7 to 1% of BW). Steers were finished on a rotationally grazed, tall fescue pasture for 116 d. Fatty acid composition of LM, s.c. adipose, and diet was determined by GLC. Total linoleic acid intake increased linearly (P < 0.01) with corn oil supplementation (90.7, 265.1, and 406.7 g in none, medium, and high, respectively). Oil supplementation linearly reduced (P < 0.05) myristic, palmitic, and linolenic acid percentage in LM and s.c. adipose. Vaccenic acid (C18:1 t11; VA) percentage was 46 and 32% greater (linear, P = 0.02; quadratic, P = 0.01) for medium and high, respectively, than none, regardless of tissue. Effect of oil supplementation on CLA cis-9, trans-11 was affected by type of adipose tissue (P < 0.01). In the LM, CLA cis-9, trans-11 isomer was 25% greater for medium than for none and intermediate for high, whereas CLA cis-9, trans-11 CLA isomer was 48 and 33% greater in s.c. adipose tissue for medium and high than for none, respectively. Corn oil linearly increased (P ≤ 0.01) trans-10 octadecenoic acid and CLA trans-10, cis-12; however, values were low (<0.35 and <0.035% of total fatty acids, respectively). Oil supplementation did not change (P > 0.05) the percentage of total SFA, MUFA, or PUFA but linearly increased (P = 0.03) n-6:n-3 ratio from 2.4 to 2.9 in none and high, respectively. Among tissues, total SFA and MUFA were greater in s.c. adipose than LM, whereas total PUFA, n-6, and n-3 fatty acids and the n-6:n-3 ratio were lower. Trans-10 octadecenoic acid, VA, and CLA trans-10, cis-12 were greater (P < 0.01) in s.c. adipose than in LM. Oil supplementation did not alter (P > 0.05) stearoyl CoA desaturase activity or mRNA expression. Corn oil supplementation to grazing steers reduced the percentages of highly atherogenic fatty acids (myristic and palmitic acids) and increased the percentages of antiatherogenic and anticarcinogenic fatty acids (VA and cis-9, trans-11 CLA). [ABSTRACT FROM AUTHOR]

Eighteen Angus steers (438 ± 4 kg of BW) were supplemented with varying levels of corn oil (0 g/kg of BW, none; 0.75 g/kg of BW, MED; or 1.5 g/ kg of BW, HI) on rotationally stocked, endophyte-free tall fescue to determine the effect of supplemental oil level on in vivo digestibility, intake, performance, and carcass traits. Pelleted cottonseed hulls were used as a carrier for the oil supplements, and all supplements were offered to steers using Calan gate feeders for individual intake determination. On d 49, each steer was dosed with a controlled-release capsule containing chromium sesquioxide, and fecal samples were obtained 12 d later over a 7-d period to estimate fecal output that, with forage, supplement, and fecal indigestible NDF concentration, was used to estimate DMI and in vivo total diet digestibility. Steers were slaughtered at the end of the 116-d grazing period, and carcass data were collected at 24 h postmortem. Total fatty acid intake linearly increased with corn oil supplementation, and forage DMI, total DMI, and total DE intake were linearly decreased (P < 0.01). The decrease in total DMI was reflected in forage substitution rates greater (P ≤ 0.01) than 1, with a trend (P = 0.09) for a greater substitution rate in HI than in MED. In vivo DM, OM, and NDF digestibility were linearly decreased (P <0.01) by corn oil supplementation. Average daily gain and final BW tended (P = 0.09) to increase linearly in response to oil level. Oil conversion (0.36 kg of BW gain/kg of corn oil) was greater (P ≤ 0.05) than zero and did not differ (P = 0.15) between MED and HI. Dressing percent (P = 0.09), carcass weight (P = 0.01), and carcass backfat thickness (P = 0.01) increased linearly with oil supplementation. No treatment effect was observed for carcass LM area, KIPH percentage, marbling score, or yield grade (P> 0.10). Oil supplementation to grazing steers linearly reduced forage DMI intake; however, animal performance was maintained and tended to be greater for oil-supplemented cattle. Oil supplementation increased carcass fat thickness and weight without altering other carcass quality parameters. [ABSTRACT FROM AUTHOR]

Twenty eight Angus (289 ± 3.8 kg) steers were used in a completely randomized design to evaluate the effect of isoenergetic supplementation of two different energy sources to steers rotationally grazing tall fescue pastures for 197 d. Steers were supplemented with either corn grain (0.52% BW; PC) or soybean hulls plus corn oil (0.45% BW + 0.10% corn oil; PO) using Calan gates for individual intake measurement. Negative (pasture only; P) and positive (85% concentrate/15% roughage; C) control diets were also included in the study to compare with the performance of the supplemented steers. Steers on PC, PO and P treatments were managed together under a rotational grazing system; whereas, C steers were maintained on an adjacent tall fescue pasture for the initial 105 d and then fed a high concentrate diet also using Calan gates. Data were analyzed using Mixed procedure of SAS; LS-means were separated using pdiff option. The ADG for PC and PO was higher (P < 0.01) than in P and lower (P < 0.01) than C. ADG tended (P = 0.09) to be greater for PC than PO during the first 105 d period but ADG did not differ among supplement sources during final 92 d or overall. Hot carcass weights for PO and PC were 36 kg greater (P < 0.01) than P and 67 kg lighter (P < 0.01) than C. However, efficiency of concentrate utilization (overall kg of gain above P/kg supplement or overall kg of gain/kg high concentrate intake) did not differ among energy supplement sources or compared to concentrate finished. Dressing percentage, s.c. fat thickness, KPH percentage and yield grade were lower (P < 0.01) for PO and PC than C and higher (P < 0.01) for PO than P. Only dressing percentage was higher for PC than P, for the other variables PC was similar (P > 0.05) to either P or PO. Marbling score, quality grade, and LMA were also lower (P < 0.01) in PO and PC than in C, but did not differ (P > 0.05) from P. Energy supplementation, regardless of energy source, to grazing steers increased performance and carcass weight but did not alter carcass quality. [ABSTRACT FROM AUTHOR]

Twenty eight Angus (289 ± 3.8 kg) steers were used in a completely randomized design to evaluate the effect of isoenergetic supplementation of two different energy sources to steers rotationally grazing tall fescue pastures for 197 d on meat quality. Steers were supplemented with either corn grain (0.52% BW; PC) or soybean hulls plus corn oil (0.45% BW + 0.10% corn oil; PO). Negative (pasture only; P) and positive (85% concentrate/15% roughage; C) control treatments were also included in the study to compare with the supplemented steers (S). Steers on C were maintained on an adjacent tall fescue pasture for the initial 105 d and then fed a high concentrate diet. At the end of the feeding period steers were slaughtered and carcass temperature and pH were determined during the first 24 h post-mortem. LM color was determined, samples obtained, and aged for a total of 1, 3, 7, 14 and 28 d for subsequent Warner-Bratzler shear force and trained sensory panel evaluation. Carcass temperature decline was slowest (P ≤ 0.05) in C than in PC, PO or P. LM pH at 3 h and 24 h postmortem was lower (P ≤ 0.01) for C than PC or P with PO being intermediate. LM lightness was higher (P ≤ 0.05) for C than PO, PC, or P and was also higher (P ≤ 0.01) for PC and PO than P. Yellowness of s.c. fat was higher (P ≤ 0.01) for PO and PC than C or P, which did not differ. WBSF was lower (P ≤ 0.05) for C than for PC and P, with PO being intermediate. Trained sensory panel ratings for tenderness and beef-flavor intensity were higher (P ≤ 0.05) for C than for PC, PO, or P. Off-flavor scores were lower (P ≤ 0.01) for C than P with PC and PO being intermediate. Oil supplementation to forage-finished steers alters muscle pH, tenderness, color and off-flavors scores; the latter two variables are also affected by corn grain supplementation. [ABSTRACT FROM AUTHOR]