Stimulation of estrous behavior in grazing female goats by continuous or discontinuous exposure to males1,2

Abstract

Two experiments were conducted during the anestrous period to determine: (1) whether males rendered sexually active by exposure to artificial long days stimulate estrous activity of female goats under grazed conditions (Exp. 1); and (2) whether continuous presence of the buck is necessary to stimulate this estrous activity (Exp. 2). In Exp. 1, 2 groups of females (n = 20/group), one in confinement and another under grazing conditions, were exposed to 4 bucks subjected to natural photoperiod (2 males/group). Two other groups of females (n = 20/group), in confinement or grazing, were exposed to 4 males treated with artificial long days (2 males/group). All groups were exposed to males for 15 d. The percentage of does detected in estrus during these 15 d was greater (P < 0.001) in the 2 groups exposed to males sexually prepared by long days (confined, 95%; grazed, 90%) than in groups exposed to males in natural photoperiod (confined, 15%; grazed, 45%). Does in Exp. 2 were allowed to graze and were exposed continuously (n = 26) or discontinuously (from 1700 to 0900; n = 26) for 18 d to males that had been stimulated to enter the breeding season by exposure to long days. The proportion of does that displayed estrous behavior in 18 d did not differ (P = 0.55) between groups (96.2 and 92.3% for continuous and discontinuous groups, respectively). The results indicate that anestrous goats managed under grazing conditions can be stimulated to express estrus by joining with males previously exposed to artificial long days. Continuous presence of the male is not necessary for this male effect.

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

“…An intense sexual behavior and strong odor of males could explain the fact that light-treated males were able to induce the reproductive activity of anestrous Alpine goats, whereas control bucks were not. The stimulatory effect of long days on the capacity of bucks to induce a male effect has already been extensively documented in local Mexican goats in the subtropics (Delgadillo et al, 2006 andRivas-Muñ oz et al, 2007), but this is the first indication that its efficacy also applies to the reputedly very seasonal Alpine breed, in which control males stimulate the reproductive activity in only a few does (this study; Chemineau et al, 1986).…”

“…In these later studies, the endocrine or sexual behavior response of the Alpine bucks subjected to these photoperiodic treatments was not described. In contrast to Alpine goats, in local subtropical Mexican does, the photoperiodic treatment of females is not necessary, and high rates of estrous and ovulatory responses were observed in does exposed to males rendered sexually active by exposure to artificially long days (Delgadillo et al, 2002;Rivas-Muñ oz et al, 2007;Fitz-Rodríguez et al, 2009). The different responses between local Mexican goats and Alpine goats to the male effect could be due to a different degree of photoperiodic inhibition of the sexual activity existing in subtropical and temperate latitudes, or to possible differences in the degree of seasonality between these breeds, or both (Chemineau et al, 1992;Delgadillo et al, 1999).…”

The male effect stimulus positively increased the ovarian and reproductive seasonality in Criollo goats irrespective of a controlled photoperiodic regime

“…Such effect seems to be independent of the maleÁ female proportion (Carrillo et al 2007) as well as continuity or discontinuity of the 'male effect' treatment (Rivas-Mun˜oz et al 2007). Although, recently, it has been more associated with 'novelty' of the male ).…”

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

“…Interestingly, the light-treated males could also stimulate the estrous behavior of female goats maintained under extensive conditions. In fact, the proportion (18/20) of females that displayed estrous behavior was higher when they were left permanently in pens and grasslands with sexually active males than with sexually inactive ones (9/20; Rivas-Muñ oz et al, 2007). In addition, a high behavioral response (.90%) was also obtained when males remained in the open pen during the day while females grazed in open range (Rivas-Muñ oz et al, 2007;De Santiago-Miramontes et al, 2008;Fitz-Rodríguez et al, 2009).…”