Male Reproductive Condition Is the Limiting Factor of Efficiency in the Male Effect During Seasonal Anestrus in Female Goats1

Abstract

Two experiments were conducted to determine whether the failure of males to induce sexual activity in goats during seasonal anestrus is due to unresponsiveness of females to male stimulus or insufficient stimulation from males. In the first study, one group of males (sexually inactive, SI; n = 4) was kept under natural photoperiod while the other (sexually active, SA; n = 4) was subjected to 2.5 mo of long days (16L:8D) and received 2 s.c. implants of melatonin. Two mo later, 2 different flocks of anovulatory goats previously separated from bucks were exposed to either SI (n = 34) or SA (n = 40) bucks. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. Of the goats exposed to SI males, only 2 ovulated, and none showed estrous behavior during the 35 days of the study. In contrast, all females (40 of 40) in contact with SA males ovulated and showed at least one estrous behavior during the first 11 days following male introduction (P < 0.001). Overall, 38 of 40 females stimulated with SA bucks were diagnosed pregnant at Day 35, according to progesterone assay (versus 0 in SI-treated group: P < 0.001). To control for a possible difference of responsiveness between flocks, the experiment was repeated 1 yr later using a single flock of goats divided into 2 groups. Again, over the first 14 days, 1 of 33 goats showed estrous behavior in the SI-treated group versus 27 of 33 in the SA-treated group (P < 0.001). Therefore, treating bucks with long days and melatonin increased their teasing capacity to induce sexual activity in females during anestrus. These results indicate that the absence of response to teasing at this time of the year is not due to female unresponsiveness, but to insufficient stimulation from the male.

Stimulation of reproductive activity in anovulatory Alpine goats exposed to bucks treated only with artificially long days

“…Recently, we found that treatment by long days followed by melatonin implants stimulates some sexual activity in Alpine bucks under temperate latitude (Delgadillo et al, unpublished results). However, the responses of Alpine males in terms of testosterone and sexual behavior were not as strong as those observed in the subtropics in this study or with local Mexican bucks (Flores et al, 2000;Delgadillo et al, 2001). The ovarian response of anestrous light-untreated Alpine does exposed to these Alpine long days and melatonintreated bucks was limited (50% of does ovulating; Delgadillo et al, unpublished results).…”

“…The intra-and interassay CV were 6% and 10%, respectively. Females with progesterone levels above 0.5 ng/ml were considered to have ovulated (Flores et al, 2000).…”

“…In contrast, in highly seasonal breeds, a weak response is observed when does are exposed to males during mid-anestrus. In these breeds, the use of the male effect is limited to some weeks preceding the breeding season (Restall, 1992;Flores et al, 2000). In the Alpine breed raised under temperate latitudes, estrous behavior and the ovulatory response of does exposed to males are high only when both males and females are submitted to a light treatment of long days followed or not by melatonin administration before teasing (Chemineau et al, 1986 andPellicer-Rubio et al, 2007).…”

Environmental and social cues can be used in combination to develop sustainable breeding techniques for goat reproduction in the subtropics

“…The photoperiod-treated males induced estrous behavior in all females (40/40) in the first 11 days after their introduction. By contrast, no behavioral activity was observed in females exposed to the light-untreated males during the same period (Flores et al, 2000). These were our first results showing that the photoperiod could be used indirectly to stimulate the sexual activity of anovulatory goats.…”

“…Several factors can modify the ovulation and estrous responses of females exposed to males, including the intensity of the sexual behavior. In fact, a major limitation of the 'male effect' is that the sexual response of females is weak or absent when it is performed during mid-seasonal anestrus, probably because of the low sexual behavior of males, which are also in rest season at this time (Restall, 1992;Flores et al, 2000;Delgadillo et al, 2006). Therefore, it was tested if this limitation of the 'male effect' could be circumvented by the use of males rendered sexually active by a previous exposure to photoperiodic treatments.…”