Effect of restricted suckling on the superovulatory response and reproductive performance in postpartum Japanese black cows.

The reproductive performance of postpartum cows is affected by factors such as suckling and nutrition. We investigated the effect of a restricted suckling period on the superovulatory response and the fertility after flushing in postpartum Japanese Black cows. Forty-seven postpartum cows were used in this study. At 7 days postpartum, the cows were divided into 2 groups: (1) continuous access to calves from birth to weaning at 3 months postpartum (ad libitum suckling group; n=20); and (2) twice daily suckling to the calves penned adjacent to them (restricted suckling group; n=27). All cows were initiated a superstimulatory treatment with a controlled internal drug releasing device and follicle stimulating hormone at 40 days postpartum. Embryos were nonsurgically collected at 7 or 8 days after estrus. After uterine flushing, the cows were again used for reproduction. There were no significant differences between the ad libitum and restricted suckling groups in terms of the numbers of transferable (6.7 ± 5.4 versus 7.9 ± 7.0) and freezable embryos (5.5 ± 4.9 versus 6.2 ± 7.0). In contrast, the interval to the first estrus after flushing in the restricted suckling group was lower (P<0.05) than that in the ad libitum suckling group (8.9 ± 5.7 days versus 27.9 ± 24.2 days). These results suggest that restricted suckling in postpartum Japanese Black cows does not affect the superovulatory response and embryo quality; however, it improves their fertility after flushing.