60896
document
Impact of a leptin single nucleotide polymorphism and zilpaterol hydrochloride on growth and carcass characteristics in finishing steers . 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 .
60897
Intervention_Pharmacological
zilpaterol hydrochloride
60898
Outcome_Physical
ultrasonic fat
60899
Participant_Condition
finishing steers .