Induction of twins in different breeds of cattle.

Two experiments were conducted examining bilateral transfer of Hereford X Angus crossbred embryos to Angus, Hereford and Hereford x Angus crossbred recipients. In Exp. 1, both virgin heifers and parous cows were used as recipients, in Exp. 2, only virgin heifers were used. No differences in production of twins due to breed of recipient was observed. In Exp. 1, heifers had as high a twinning rate and proportion of pregnancies carried to term as cows. About 9% of the heifers in Exp. 2 experienced late gestation abortion (based on recipients pregnant at 42 d), a problem which was not observed among heifers in Exp. 1. No association between body weight at transfer and abortion was observed. Twin pregnancy was associated with a higher incidence of retained placentas (Exp. 1, P less than .05; Exp. 2, P less than .10), lower birth weight/calf (P less than .01 in both experiments) and shorter gestation period (P less than .01 in both experiments). Calf mortality at birth was similar among twins and singles and, in Exp. 2, a lower (P less than .02) incidence of dystocia was observed among heifers giving birth to twins than among those with single calves. The results of these experiments indicate that both beef heifers and beef cows of three common breed types are capable of maintaining twin pregnancies and successfully producing twins.