Maternal influences on growth of twin and single calves.

Milk production was measured at 28-d intervals by the calf weight change method in 30 dams with twins and in 28 dams with single calves. Average adjusted 170-d weaning weights for twins were between 41 and 38 kg less than for singles (depending on linear contrast). Yet dams with twins weaned between 91 and 97 kg more calf and produced substantially more milk. Significant dam breed and parity differences in calf growth and weaning weight were observed among twins. Dam breeds ranked in the order of decreasing productivity were Hereford-Angus crossbred, Angus and Hereford. Cows outproduced heifers. Among singles, such differences were small. As indicated by linear contrasts, maternal effects were larger in twins than in singles; however, these differences were generally not significant. Only milk production in the first half of lactation by dams with twins was found to be a significant predictor of calf growth and weaning weight. For every 1-kg increase in 6-h milk production in early lactation, 170-d adjusted weaning weight of twins increased (P less than .01) by 18.8 kg. Among singles, regression estimates for growth on milk yield were small and nonsignificant.