Biostimulatory effects of estrous cows and bulls on resumption of ovarian activity in postpartum anestrous zebu (Bos indicus) cows in the humid tropics.

摘要

60 postpartum (2-3 months after calving) zebu cows in anoestrus >4 years of age, each of which was suckled by a calf, were subjected to the following treatments (start of treatment = day 1): (1) exposed to a progestogen treated female (approximately3 cows per progestogen-treated cow) and a bull from day 1 to day 42; (2) exposed to a progestogen-treated female from day 1 to day 42 and exposed to a bull from day 21 to day 42; (3) exposed to a bull from day 21 to day 42. The cows in groups 1 and 2 were induced in oestrus with Syncro-Mate and were in oestrus at the start of the experiment. Resumption of ovarian activity before day 21 occurred in 57 (8/14), 19 (6/31) and 7% (1/15) of the cows in the 3 groups respectively (P<0.05). Between days 21 and42, after the introduction of the bull to groups 2 and 3, an additional 32 (10/31) and 33% (5/15) of cows in the 2 groups respectively resumed ovarian activity. None of the cows in group 1 resumed ovarian activity between day 21 and day 42.