Gregory K E, Echternkamp S E, Dickerson G E, Cundiff L V, Koch R M, Van Vleck L D
Roman L. Hruska U.S. Meat Anim. Res. Center, U.S. Department of Agriculture, Clay Center, NE 68933.
J Anim Sci. 1990 Oct;68(10):3133-44. doi: 10.2527/1990.68103133x.
An evaluation of natural twinning in beef cattle revealed that cows birthing twins had shorter (P less than .01) gestation lengths, more (P less than .01) retained placentas, more (P less than .01) dystocia, more (P less than .01) days to estrus, lower (P less than .01) conception rates and more (P less than .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of calves reared (1 vs 2) in cows birthing twins. Survival at birth was greater (P less than .01) for single- than for twin-born calves, but twins and singles did not differ (P greater than .05) in postnatal survival. When dystocia was experienced, calf survival at birth was 95% vs 73% for singles vs twins compared with 99% vs 92% when no dystocia was experienced. Calves born twins were lighter (P less than .01) at birth, 100 d and 200 d, but twins and singles did not differ in postweaning gains. Total calf weights at 100 d per cow calving were 12% greater (P less than .01) in cows birthing twins vs singles when twin calves reared by foster dams were excluded. The potential increase in cow productivity for total calf weight at 100 d is 40% if calf survival rates of twins with dystocia relative to survival rates of twins without dystocia were comparable to survival rates of singles with and without dystocia, and if cows birthing twins were fed and managed to obtain conception rates equal to those of cows birthing singles. Identification of cows gestating twins to provide for their higher prepartum nutritive requirements and calving assistance at parturition is necessary to make twinning in cattle an economically viable technology.
一项对肉牛自然孪生情况的评估显示，产双胎的母牛妊娠期较短（P<0.01），胎盘滞留较多（P<0.01），难产较多（P<0.01），发情天数较多（P<0.01），受胎率较低（P<0.01），怀孕天数较多（P<0.01），相比产单胎的母牛。产双胎的母牛中，饲养犊牛数量（1头对2头）对发情天数、受胎率和怀孕天数没有影响。单胎犊牛出生时的存活率高于双胎犊牛（P<0.01），但双胎和单胎犊牛产后存活率没有差异（P>0.05）。出现难产时，单胎犊牛出生时的存活率为95%，双胎犊牛为73%，而未出现难产时，单胎犊牛为99%，双胎犊牛为92%。双胎出生的犊牛在出生时、100日龄和200日龄时体重较轻（P<0.01），但双胎和单胎犊牛断奶后生长速度没有差异。当排除由寄养母牛饲养双胎犊牛的情况时，每头产犊母牛所产犊牛在100日龄时的总重量，产双胎的母牛比产单胎的母牛高12%（P<0.01）。如果难产双胎犊牛的存活率相对于无难产双胎犊牛的存活率与有难产和无难产单胎犊牛的存活率相当，并且如果产双胎的母牛在饲养和管理上能使其受胎率与产单胎的母牛相同，那么母牛在100日龄时犊牛总重量的生产性能潜在提高可达40%。识别怀有双胎的母牛，以满足其更高的产前营养需求并在分娩时提供助产，对于使牛的孪生成为一种经济可行的技术是必要的。
