Reproductive, growth, feedlot, and carcass traits of twin vs single births in cattle

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Abstract
The frequency of fraternal twin births has increased 3.1% per year to an annual rate of 50 to 55% twins in a selected herd of cattle at the U. S. Meat Animal Research Center. Because twin ovulations are the first prerequisite for fraternal twins, breeding value for twinning was predicted by repeated measures of ovulation rate in all yearling heifers and of twinning rate in selected females. Gestation length was shorter (276.1 vs 283.1 d; P < 0.01) and birth weight was lower (37.2 vs 47.2 kg; P < 0.01) for twin vs single calves, respectively, but total birth weight (live) was increased 53.1% for twins. Respective weaning weights (200-d weight) were 232 vs 259 kg (P < 0.01). Number of calves weaned per cow calving was 0.89 for single, 1.52 for twin births, and 1.80 for triplets (P < 0.01); total weaning weight was increased 48.1% for twins and 66.8% for triplets. Single-born male calves gained 74 g more per day than twin-born males from birth to 200 d and 45 g more per day from 200 d to slaughter; males were weaned at an average of 172 d of age and were castrated at 200 d. Differences in carcass traits between twin and single steers were small. Freemartins, 96% of the females born co-twin to a male, did not differ from intact twin females in growth traits, but freemartins had higher (P < 0.05) scores for marbling and a greater (P < 0.05) percentage of carcasses were USDA Choice or higher quality grade. Efficiency constraints to twin births were increased (P < 0.01) incidence of retained placentas (27.9 vs 1.9%), of dystocia (46.9 vs 20.6%), and of perinatal calf mortality (14.1 vs 3.6%); calf survival at 200 d of age was 12.4% less for twin calves. Dystocia of twins resulted primarily from malpresentation of one or both calves at birth. Fertility was reduced 11.6% (P < 0.01) after a twin birth and 7.3% (P < 0.05) after a retained placenta, but the effect of twinning on fertility varied significantly (P < 0.01) among years and seasons. Collectively, twinning increased productivity at weaning by 54.2 kg (or 28.3%) per cow exposed at breeding. Copyright © 2002. American Society of Animal Science . ©2002 American Society of Animal Science

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