Evidence that Refractoriness to Long and Short Daylengths Regulates Seasonal Reproductive Transitions in Mediterranean Goats

Abstract

Two experiments were performed to assess the role of refractoriness to long and short daylengths in the timing of seasonal reproductive transitions in Mediterranean Malagueña goats. In the first experiment, intact adult does were either maintained under natural photoperiod conditions (NP; n = 5) or exposed to a constant long day photoperiod (LD - 16 h light/day; n = 5) from June to December 2005. In the second experiment, does were maintained either under NP conditions (n = 5) or received a series of subcutaneous melatonin implants (MI) from December 2005 to June 2006 to mimic a short day signal (n = 5). In both experiments, ovulatory activity was assayed by determining progesterone concentrations in blood samples collected twice per week. The onset of seasonal ovulatory activity did not differ (p > 0.05) between the LD and NP does (3 October ±5 days and 23 September ±3 days respectively). The simulated short days did not modify (p > 0.05) the timing of the end of ovulatory activity. The MI does become anoestrus at the same time (1 March ±9 days) as their NP counterparts (23 February ±8 days). These results indicate that, in Malagueña does, the onset and offset of anoestrus are not driven by photoperiod changes but appear to be the result of long and short day refractoriness respectively. An endogenous circannual rhythm may therefore be involved in regulating seasonal reproductive changes in these animals.

Effect of Non-Genetic Factors on Reproduction of Extensive versus Intensive Florida Dairy Goats

“…In addition, goats kidding in summer often undergo a decrease in milk production in winter being mated in advance and consequently reducing KI. Similar findings were presented in two other Spanish goat breeds: the Payoya goat [ 53 ] and Malagueña goat [ 54 ]. Besides, the current results exactly match those obtained by [ 55 ] in northwestern Croatia, with a mean KI significantly longer in winter and spring than in summer and autumn for Boer goats.…”

Male goat vocalizations stimulate the estrous behavior and LH secretion in anestrous goats that have been previously exposed to bucks

“…In goats, the breeding season is characterized by a succession of estrous and ovulatory cycles of about 21 days occurring approximately from September to February, while the seasonal anestrous lasts from March to August (Chemineau et al, 1992;Duarte et al, 2008;Fatet et al, 2011). This annual reproductive cycle is mainly controlled by photoperiod (Duarte et al, 2010;Gebbie et al, 1999;Gómez-Brunet et al, 2010). However, socio-sexual interactions can modify this reproductive seasonality.…”