Induction of sexual activity in lactating anovulatory female goats using male goats treated only with artificially long days1

Abstract

Two experiments were conducted to determine the response of Creole male goats treated with long days and melatonin implants, and the response of the anovulatory does to male effect using males treated only with artificially long days. All animals were allocated to open sheds. In Exp. 1, one group of males was under natural photoperiod (CG; n = 7); the second group was submitted to 2.5 mo of long days followed by the insertion of two s.c. melatonin implants (LD+MEL; n = 7); the third group was subjected only to 2.5 mo of long days (LD; n = 7). Testicular weight was measured every 2 wk. Plasma testosterone concentrations were determined weekly. A treatment x time interaction was detected (P < 0.001) for testicular weight and plasma testosterone concentration. In the LD+MEL and LD groups, testicular size and plasma testosterone levels varied in a similar way, but differed from those observed in CG (P < 0.001). In this latter group, testicular weight displayed seasonal variations and peaked in June, whereas in treated groups this peak occurred in March. In CG, testosterone varied in a seasonal manner and plasma concentrations increased in June and remained elevated throughout the study. In experimental groups, testosterone increased in February and peaked in March. In Exp. 2, one group of males was left under natural photoperiod (CG, n = 5) and the other one was submitted to 2.5 mo of artificially long days (LD, n = 4). On March 16, two control and two treated males were put in contact with 20 and 19 females, respectively. Sexual behavior of the bucks was observed during the 5 d following male introduction. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. The anogenital sniffing, nudging, and mount instances registered in LD-treated males were greater than those observed in CG (P < 0.05). Of the does exposed to CG, none ovulated and only two of 20 females displayed estrous behavior. All does in contact with LD-treated males ovulated and showed at least one estrous behavior during the 15 d following joining (P < 0.001). These results indicate that the sexual activity of male goats from subtropical latitudes can be induced using only artificially long days. In addition, males treated in this way are capable of stimulating sexual activity in anovulatory females by the male effect.

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

“…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).…”

Reproductive performance of Lacaune dairy sheep exposed to artificial long days followed by natural photoperiod without and with additional progestagen treatment during the nonbreeding season

“…In ewes, long days are provided by artificial illumination, whereas short days are simulated through melatonin implants [7,8]. As an alternative to the melatonin application, the exposition to naturally short day length has been shown to also be effective in the goat [8][9][10]. In dairy sheep, however, there are no published reports on the efficacy of light programs without melatonin application to induce cycling activity during the nonbreeding season.…”

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

“…For this purpose, two light-treated and two control bucks were placed with anovulatory goats maintained in open pens. The proportion of females that displayed estrous behavior was greater in those exposed to the light-treated bucks (19/19) than in those exposed to lightuntreated ones (2/20; Delgadillo et al, 2002). Interestingly, the light-treated males could also stimulate the estrous behavior of female goats maintained under extensive conditions.…”

“…Control males remained in a shaded open pen under a natural photoperiod throughout the experiment. In both long-day treated groups, plasma testosterone concentrations did not differ and were higher than in controls from February to April, during the nonbreeding season, indicating that the long-day treatment stimulated the endocrine testes activity, and that melatonin was not necessary for this stimulation (Figure 6; Delgadillo et al, 2002). Then, we tested the efficiency of the only longday treated bucks to stimulate the sexual activity of the anestrous goats.…”

“…The high response induced by the light-treated males could be due to the fact that photoperiodic treatment stimulates testosterone secretion, the odor of males and their sexual behavior, improving the quality of signals provided by the males to does during the 'male effect' (Delgadillo et al, 2006;Murata Months Figure 6 Changes (mean 6 s.e.m.) in plasma testosterone concentrations in local male goats from subtropical Mexico subjected to natural photoperiodic variations (J, or to 2.5 months of artificial long days (16 h of light/day) from November 1, and then treated with two s.c. melatonin implants (n) or exposed to natural short days (') (adapted from Delgadillo et al (2002)). …”