Male effect in seasonally anovulatory lactating goats depends on the presence of sexually active bucks, but not estrous females

A study was conducted in subtropical northern Mexico (26°N) to determine whether the presence of estrous females can improve the response of seasonally anovulatory goats to the introduction of bucks in the group. The induction of estrous activity was studied in three groups of anovulatory lactating goats during seasonal anestrus. These females were of the Mexican Creole breed. In the control group (sexually inactive (SI), n=20), two control (SI) bucks exposed to normal seasonal daylength variations were used. In the second group (SI+E, n=20+3), two control males were also used, but in addition, three females of the group were in estrus at the time of male introduction. In the third group (sexually active, SA+E, n=19+4), anovulatory females were exposed to two bucks made sexually active by exposure to 2.5 months of long days (16L:8D) followed by two subcutaneous 18 mg melatonin implants, and four estrous females were also present when introducing the bucks. In all groups, males were introduced on 15 March and estrous detection was conducted twice daily for 15 days. The sexual activity of the bucks was observed from 08:00 to 10:00 h during the first five days of exposure to females. More females displayed estrous behavior in the first 15 days following the introduction of the males in the SA+E group (18/19) as compared with the SI or SI+E groups (2/20 and 0/20, respectively; P