Jones S D, Newman J A, Tong A K, Martin A H, Robertson W M
J Anim Sci. 1986 Jun;62(6):1602-8. doi: 10.2527/jas1986.6261602x.
A total of 144 male crossbred calves were allocated to four management treatments (bulls; steers; bulls implanted with zeranol at 100 d of age and re-implanted at 69, 93 and 56 d thereafter; bulls implanted with zeranol at 168 d of age and re-implanted at 93 and 56 d thereafter), and two pre-slaughter shipping treatments (minimum pre-slaughter stress with cattle shipped and slaughtered within 4 h of leaving the feedlot pen; moderate pre-slaughter stress with cattle mixed, trucked 160 km and slaughtered up to 24 h of leaving the feedlot pen) in a 4 X 2 factorial arrangement. Management treatment had no significant effect on carcass pH (45 min), carcass muscle temperature (45 min), or peak shear-force of cooked longissimus muscle. Steers had significantly lower dressing percentage, warm-carcass weight, hide weight and carcass-lean content, but higher marbling score, fat thickness and intramuscular-fat content than all treatments with bulls. Minimum pre-slaughter stress resulted in significantly lower dressing percentage, warm-carcass weight, and carcass pH (45 min), but generally had no effect on carcass tissue-yield measurements compared with the moderate stress treatment. Implanted bulls produced carcasses with significantly darker meat, higher 24-h pH and lower meat expressible juice than bulls and castrates for the moderate pre-slaughter stress treatment. These results provide evidence that zeranol implantation in bulls had a minor influence on carcass characteristics, and did not reduce the incidence of dark-cutting carcasses in young bulls subjected to moderate pre-slaughter shipping stress.
总共144头雄性杂交犊牛被分配到四种管理处理方式（公牛；阉牛；100日龄时植入玉米赤霉醇且此后在69、93和56日龄时再次植入的公牛；168日龄时植入玉米赤霉醇且此后在93和56日龄时再次植入的公牛），以及两种宰前运输处理方式（宰前应激最小，牛只在离开饲养场围栏后4小时内运输并屠宰；宰前应激适中，牛只混合、运输160公里并在离开饲养场围栏后长达24小时内屠宰），采用4×2析因设计。管理处理方式对胴体pH值（45分钟时）、胴体肌肉温度（45分钟时）或熟制背最长肌的峰值剪切力没有显著影响。阉牛的屠宰率、热胴体重、皮重和胴体瘦肉含量显著低于所有公牛处理组，但大理石花纹评分、脂肪厚度和肌内脂肪含量高于所有公牛处理组。与中等应激处理相比，最小宰前应激导致屠宰率、热胴体重和胴体pH值（45分钟时）显著降低，但对胴体组织产量测量指标通常没有影响。对于中等宰前应激处理，植入玉米赤霉醇的公牛生产的胴体肉色明显更暗，24小时pH值更高，肉的可挤出汁液更低。这些结果表明，在公牛中植入玉米赤霉醇对胴体特性影响较小，并且不会降低经受中等宰前运输应激的年轻公牛中黑切肉胴体的发生率。
