The ovarian and hormonal response of the ewe to stimulation by the ram early in the breeding season

Importance of intense male sexual behavior for inducing the preovulatory LH surge and ovulation in seasonally anovulatory female goats

“…Taken together, the results of the current study and those of Vielma et al [5], the two studies enable a full comparison of the endocrine and ovulatory responses induced by nonsedated and sedated bucks in seasonal anestrous goats. The characteristics of the preovulatory LH surge observed in our present study coincide with those previously described by others and occurred approximately 36 hours after the introduction of the non-sedated males [7,25,28]. In accordance with previous studies [29,30], our results further indicate that the female goats exposed to the nonsedated males ovulated approximately 20 to 24 hours after the preovulatory LH surge.…”

Effect of the introduction of rams during the anoestrous season on the pulsatile secretion of LH in ovariectomized ewes

“…In addition to an increase in the basal levels of LH, entire anoestrous ewes experience a preovulatory surge 6-52 h after the introduction of rams (Oldham et al, 1978;Knight, Peterson & Payne, 1979;Martin et al, 1980b;Poindron et al, 1980). How this is brought about is not known but it has been suggested that the surge may be induced by a direct action of the ram stimulus on the hypothalamic mechanisms controlling LH secretion, so bypassing the normal system of positive feedback by oestrogen (Oldham et al, 1978;Knight et al, 1979 Statistical analysis.…”

“…How this is brought about is not known but it has been suggested that the surge may be induced by a direct action of the ram stimulus on the hypothalamic mechanisms controlling LH secretion, so bypassing the normal system of positive feedback by oestrogen (Oldham et al, 1978;Knight et al, 1979 Statistical analysis. The basal levels of LH, before and after the introduction of the rams, were calculated as the mean of the 10 lowest points in the profile.…”

Biostimulation: Innovative Tool to Improve Reproductive Efficiency in Farm Animals

“…During normal breeding season the introduction of males enhance the onset of oestrous cycles in seasonally anoestrus ewes (Knight et al, 1978;Pearce and Oldham, 1984) and goats (Shelton, 1960). In swine also the "boar effect" has been well documented.…”