Effects of twinning on dystocia, calf survival, calf growth, carcass traits, and cow productivity

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 0.01) 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 0.01), 150 d (14.8%, P 0.01), and 200 d (15.2%, P 0.01). Survival of calves with no dystocia was higher than survival of calves with dystocia: 8.6% (P 0.01) at birth, 10.8% (P 0.01) at 72 h, 12% (P 0.01) at 150 d, and 12.2% (P 0.01) at 200 d. The effect of dystocia on survival was greater (P 0.01) 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 0.01) at birth and 28 kg heavier (P 0.01) 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 0.01) 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 0.01) 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 0.01) per day from 200 d to slaughter and 57 g more (P 0.01) 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