Gregory K E, Echternkamp S E, Cundiff L V
Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933, USA.
J Anim Sci. 1996 Jun;74(6):1223-33. doi: 10.2527/1996.7461223x.
This paper reports results from a long-term experiment with a primary objective to increase twinning rate in cattle at the Roman L. Hruska U.S. Meat Animal Research Center. Survival of singles was 13% higher (P < .01) than that of twins at birth, and the difference in survival in favor of singles was of similar magnitude at 72 h (12.9%, P < .01), 150 d (14.8%, P < .01), and 200 d (15.2%, P < .01). Survival of calves with no dystocia was higher than survival of calves with dystocia: 8.6% (P < .01) at birth, 10.8% (P < .01) at 72 h, 12% (P < .01) at 150 d, and 12.2% (P < .01) at 200 d. The effect of dystocia on survival was greater (P < .01) in twins than in singles at birth and at 72 h. Least squares means for dystocia were 20.4% in singles compared with 42.2% in twins. Most of the dystocia in singles resulted from a traction requirement (84.7%) of normal presentations, whereas most of the dystocia in twins (77.8%) resulted from malpresentations, with 59.2% of the malpresentations accompanied with a requirement for traction. Survival in singles ranged from 10.7% to 15.3% greater than in twins at different ages when there was no requirement for assistance in either singles or twins. Calves born as singles were 8.8 kg heavier (P < .01) at birth and 28 kg heavier (P < .01) at 200 d than calves born and reared as twins. Calf weight produced per cow calving was 53.1%, 54.7%, and 58.4% greater (P < .01) at birth, 150 d, and 200 d, respectively, in cows producing twins than in cows producing singles. Cows producing twins had 65.2% more (P < .01) live calves at 200 d than cows producing singles. Single male calves gained 74 g more per day than twin males from birth to 200 d, 45 g more (P < .01) per day from 200 d to slaughter and 57 g more (P < .01) per day from birth to slaughter. Differences between twin and single males in carcass traits were small. A sample of steers from the Twinning Project gained significantly faster and produced significantly more desirable carcasses than a sample of steers from a high performance reference population. Freemartins did not differ (P < .05) from normal females in growth traits, but freemartins had higher (P < .05) scores for marbling with a higher percentage (P < .05) of USDA Choice or better quality grade carcasses and lower estimated percentage retail product.
本文报告了在美国罗马L. 赫鲁斯卡肉类动物研究中心进行的一项长期实验的结果，该实验的主要目的是提高牛的双胎率。单胎出生时的存活率比双胎高13%（P <.01），在出生后72小时（12.9%，P <.01）、150天（14.8%，P <.01）和200天（15.2%，P <.01）时，单胎在存活方面的优势幅度相似。顺产犊牛的存活率高于难产犊牛：出生时高8.6%（P <.01），72小时时高10.8%（P <.01），150天时高12%（P <.01），200天时高12.2%（P <.01）。难产对双胎存活率的影响在出生时和72小时时比单胎更大（P <.01）。单胎难产的最小二乘均值为20.4%，而双胎为42.2%。单胎中的大多数难产（84.7%）是由于正常胎位的牵引需求，而双胎中的大多数难产（77.8%）是由于胎位不正，其中59.2%的胎位不正伴有牵引需求。在不同年龄段，当单胎和双胎都不需要助产时，单胎的存活率比双胎高10.7%至15.3%。单胎出生时比双胎重8.8千克（P <.01），200天时重28千克（P <.01）。产双胎的母牛在出生时、150天和200天时，每头母牛产犊的犊牛体重分别比产单胎的母牛高53.1%、54.7%和58.4%（P <.01）。在200天时，产双胎的母牛比产单胎的母牛多65.2%（P <.01）的存活犊牛。从出生到200天，单胎雄性犊牛每天比双胎雄性犊牛多增重74克，从200天到屠宰时每天多增重45克（P <.01），从出生到屠宰时每天多增重57克（P <.01）。双胎和单胎雄性在胴体性状上的差异很小。双胎项目中的一组阉牛比高性能参考群体中的一组阉牛生长速度明显更快，胴体质量也明显更优。自由马丁牛在生长性状上与正常母牛没有差异（P <.05），但自由马丁牛的大理石花纹评分更高（P <.05），美国农业部精选级或更高质量等级胴体的百分比更高（P <.05），零售产品估计百分比更低。
