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Walter L.J.,West Texas A&M University | Gasch C.A.,West Texas A&M University | Mcevers T.J.,West Texas A&M University | Hutcheson J.P.,Merck Animal Health | And 3 more authors.
Journal of Animal Science | Year: 2014

Beef cattle from 3 independent studies conducted in the Texas Panhandle (Exp. 1: n = 3,906 and Exp. 2: n = 4,000) and southern Idaho (Exp. 3; n = 542) were used to investigate the association of pro-melanin concentrating hormone (PMCH) genotype with beef carcass quality and yield attributes. Tissue samples were collected from each animal to determine which PMCH allele they expressed (Trial 1: AA, 62.60%; AT, 32.05%; and TT, 5.35%; Trial 2: AA, 64.33%; AT, 31.07%; and TT, 4.60%; Trial 3: AA, 65.87%; AT, 29.34%; and TT, 4.80%). Twenty-four hours after harvest, carcass attributes were evaluated for all carcasses and longissimus dorsi steak samples were allocated from a subset of carcasses in Exp. 2 (n = 352; AA, 49.43%; AT, 28.98%; and TT, 21.59%) and each carcass in Exp. 3. Warner-Bratzler shear force measurements were determined for each steak after aging for 7, 14, or 21 d postmortem. Carcasses from Exp. 1 and 2 expressing the AA genotype had greater (P < 0.01) 12th rib subcutaneous (s.c.) fat depth and marbling scores, concurrent with smaller (P < 0.01) LM area than carcasses of AT and TT genotypes. Subsequently, carcasses expressing the AA genotype were represented by a greater (P < 0.02) proportion achieving Prime and Premium Choice quality grades, and a lesser (P < 0.01) proportion grading Select or Standard. In all trials, carcasses of the AA genotype had greater (P < 0.04) calculated yield grades than carcasses of the TT genotype. Carcass composition was associated with PMCH genotype evident by calculated empty body fat differences (P < 0.04) between AA and TT cattle in Exp. 1 and 3, and differences (P < 0.01) among all 3 genotypes in Trial 2. Shear force data on 7-d postmortem aging tended (P = 0.06) to favor cattle of the AA genotype in Exp. 2. However, additional aging to 14 or 21 d minimized any tenderness differences. These data illustrate the potential relationship that may exist among PMCH genotypes and indicators of carcass composition. © 2014 American Society of Animal Science. All rights reserved. Source


Kononoff P.J.,University of Nebraska - Lincoln | James S.T.,Quantum Genetix Canada Inc | Deobald H.M.,Quantum Genetix Canada Inc | Deobald J.L.,Quantum Genetix Canada Inc | Marquess F.L.S.,Quantum Genetix Canada Inc
Journal of Animal Science | Year: 2013

A total of 4,178 steers (mean initial BW = 403.9 ± 16.04 kg) were used to test the interactive effects, if any, of leptin R25C genotypes (CC, CT, or TT) and zilpaterol hydrochloride (ZH) feeding duration on growth performance and carcass traits. Steers were blocked by arrival at the feed yard, genotyped for the leptin SNP, allotted to genotype-specific pens (90 steers/pen), and assigned randomly within genotype and block to 0 or 21 d of dietary ZH. All pens within a block were slaughtered on the same day (132.1 ± 10.9 d on feed). Final BW of steers fed ZH was 6.0 kg heavier (P = 0.008), and ZH-fed steers had greater (P = 0.003) ADG than steers not fed ZH. Feeding ZH decreased DMI in steers with increased frequency of the T allele (9.67, 9.53, and 9.28 kg/d for CC, CT, and TT, respectively), but DMI increased with the frequency of the T allele (9.68, 9.90, and 10.1 kg for CC, CT, and TT, respectively) when ZH was not fed (leptin genotype × ZH, P = 0.011). At the conclusion of the study, ultrasonic fat was greatest for TT steers (11.4 ± 0.28 mm) and least (P = 0.003) for CC steers (11.0 ± 0.25 mm). Regardless of ZH-feeding duration, TT steers produced a greater (P = 0.006) percentage of USDA yield grade (YG) 4 or higher carcasses (5.4 vs. 2.7%) and a lesser (P = 0.006) percentage of YG 1 carcasses (17.7 vs. 26.8%) than CC steers. In addition, ZH-fed steers produced a greater (P < 0.001) percentage of USDA YG 1 carcasses (25.9 vs. 16.2%) and a lesser (P < 0.001) percentage of YG 4 or higher carcasses (1.6 vs. 6.0%) than steers fed the control diet. Marbling scores and the percentage of carcasses grading USDA Choice and Prime were greater in TT than CC steers when fed diets devoid of ZH, but both marbling and quality grades did not differ among leptin genotypes when fed ZH for 21 d (leptin genotype × ZH, P ≤ 0.03). The amount of HCW gain tended to be less (P = 0.095) for steers of the TT genotype (12.7 kg) than either CC (16.3 kg) or CT (17.0 kg) genotypes. Results indicated that leptin R25C genotype impacted most traits associated with fatness whereas feeding ZH for 21 d affected HCW and ADG positively but impacted feed intake, marbling, and USDA quality grades negatively. © 2013 American Society of Animal Science. All rights reserved. Source


Kononoff P.J.,University of Nebraska - Lincoln | James S.T.,Quantum Genetix Canada Inc | Marquess F.L.S.,Quantum Genetix Canada Inc
Journal of Animal Science | Year: 2014

A total of 2,958 steers (mean initial BW = 549.6 ± 3.88 kg) were used to test for the interactive effects, of leptin R25C genotypes (CC, CT, or TT) and feeding of ractopamine hydrochloride (RH) on growth performance and carcass traits. Before application of the drug, steers were blocked by arrival at the feed yard, genotyped for the leptin SNP, allotted to genotype-specific pens, and assigned randomly within genotype and block to 0 or 28 d of dietary RH. All pens within a block were slaughtered on the same day. Final BW of steers fed RH was 9.1 kg heavier (P < 0.001), and RH-fed steers had greater (P < 0.001) ADG and greater (P = 0.001) HCW than steers not fed RH. Feeding RH did not (P = 0.723) affect DMI but it did increase (P = 0.001) with increased frequency of the T allele (8.62, 8.70, and 8.82 kg/d for CC, CT, and TT, respectively). Consistent with the effect of leptin on DMI, increased frequency of the T allele also positively affected 12th rib fat (P = 0.001) and empty body fat (P = 0.001). Regardless of RH-feeding duration, TT steers produced a greater (P = 0.001) percentage of USDA yield grade (YG) 4 or higher carcasses (6.46 vs. 2.98%) and a lesser (P = 0.023) percentage of YG 1 carcasses (16.0 vs. 21.9%) than CC steers. In addition, RH-fed steers produced a lesser (P = 0.034) percentage of USDA YG 4 or higher carcasses (3.70 vs. 5.31%) and a lesser percentage (P = 0.019) of USDA Choice or higher carcasses (57.5 vs. 62.5%) than steers fed the control diet. Results indicated that leptin R25C genotype impacted most traits associated with fatness, whereas feeding RH for 28 d affected HCW and ADG positively but impacted marbling and USDA quality grades negatively. © 2014 American Society of Animal Science. All rights reserved. Source


Kononoff P.J.,C220j Animal Science | James S.T.,Quantum Genetix Canada Inc | Deobald H.M.,Quantum Genetix Canada Inc | Deobald J.L.,Quantum Genetix Canada Inc | And 2 more authors.
Canadian Journal of Animal Science | Year: 2015

Crossbred steers were used in a randomized complete block design to evaluate a feedlot cattle sorting system. The sorting system combined information on live body weight, ultrasound fat thickness, coat color, and genotype on the leptin R25C genotype. Using described sorting criteria, a total of four groups (Groups 1_4) of cattle were created along with a randomly selected unsorted control (Group 5), with Groups 1 through 5 representing experimental treatments, and placed in one of five pens within each block. Block was replicated 10 times thus n equaled 50. All cattle were administered zilpaterol hydrochloride except Group 3, which we hypothesized would have a greater proportion of cattle reaching a higher value Quality Grade, and as a result administered ractopamine hydrochloride. The initial bodyweight of cattlewas similar (P=0.426) between the control Group andGroups 1-4. Initial fat, as measured by ultrasound, was also observed to be similar (P=0.256) between these two groups. Overall, when cattle included in Groups 1-4 were compared with Group 5, hot carcass weight was greater (P=0.040), while the proportion of excessively heavy weight carcasses was less (P=0.049). Additionally, hot carcass weight gain tended (P=0.096) to be higher for Groups 1-4 compared with Group 5. No differences (P³0.129) were observed for calculated yield grade. On average, cattle included in the Sorting Groups 1-4 returned $23 more per head than those in Group 5. © 2015, Agricultural Institute of Canada. All rights reserved. Source

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