COMPARATIVE PRODUCTIVITY OF COWS AFTER RECEIVING TWO EMBRYOS AT TRANSFER

Embryos were transferred surgically to each uterine horn of 31 recipient cows. Fourteen (45%) became pregnant. Nine of the pregnant recipients calved twins for a rate of 64% twins per pregnancy. Embryos were obtained from nine donors by nonsurgical flushing, with the resulting single and twin calves offspring of six of these. Donors were crossbreds of varying percentage of Charolais, Chianina, Maine Anjou, Simmental and Holstein; service sires were Charolais, Limousin or Maine Anjou and the calves were therefore 2-, 3- or 4-way crosses. Recipients included a wide range of crosses of breeds, varying in milk yield and mature weight. In addition to the twins produced by transfer, an additional six sets of twins were born during the same period to cows bred by artificial insemination (AI). Single and twin calves produced by AI service were sired by bulls of breeds similar in mature weight to that of the dam. At calving, 79% of the twinning cows required assistance compared to 29% of the single bearing cows. T...