Importance of non-olfactory ram stimuli in mediating ram-induced ovulation in the ewe

• Published in: Journal of reproduction & fertility Vol. 84; no. 1; pp. 333 - 339
• Main Authors: Pearce, G.P, Oldham, C.M
• Format: Journal Article
• Language: English
• Published: England Society for Reproduction and Fertility 01.09.1988
• Subjects: Animals; ewes; Female; Male; Ovary - physiology; ovulation; Ovulation Induction; rams; Reproduction; Seasons; Sheep - physiology; stimulation
• ISSN: 0022-4251; 1470-1626; 1741-7899
• DOI: 10.1530/jrf.0.0840333

In Exp. 1, 4 groups of 50 recently weaned ewes were exposed to various degrees of contact with rams for 65 days, followed by exposure to novel rams for 4 days. Ovarian activity in the ewes was determined by laparoscopy on Days 29, 65 and 69 of treatment. There were no treatment differences in the percentage of ewes ovulating on Day 4 whereas by Day 29 more ewes in clear fenceline and full ram contact were ovulating compared to controls ( P < 0·05, P < 0·001). After 65 days ovarian activity was significant only in those ewes in full contact with rams ( P < 0·001). Between 89 and 95% of ewes remaining anovulatory after 65 days ovulated after 4 days of full contact with novel rams. In Exp. 2, 4 groups of about 30 anovulatory ewes were exposed to various degrees of contact with rams for 5 days. Ovarian activity was assessed before and after treatment by laparoscopy. After 5 days, more ewes were ovulating in response to full ram contact than in any other treatment ( P < 0·05) and more ewes in fenceline contact with rams or with rams plus ewes were ovulating than in the isolated control treatment ( P < 0·01). In Exp. 3, 6 groups of about 40 anovulatory ewes were exposed to face masks with and without rams' wool and/or various degrees of contact with rams for 5 days. More ewes were ovulating after 5 days in the group in full physical contact with rams than in any other group ( P < 0·01). Ram contact through a clear fence either with or without masks stimulated more ewes to ovulate than masks alone or isolation from rams ( P < 0·01). The additional exposure to rams' wool did not increase the percentage of ewes ovulating in response to fenceline ram contact or masks alone but exposure to masks themselves with or without rams' wool did stimulate ovulation compared to isolated controls ( P < 0·05, P < 0·01 respectively). These results indicate that fenceline ram contact was effective in inducing ovulation in a high proportion of seasonally anovulatory ewes but less effective in lactationally anovulatory ewes. Furthermore, maximum stimulation of ovulation required full physical contact with rams in all cases. Visual and tactile/behavioural stimuli from the ram therefore appear most important in mediating the ram effect whereas olfactory cues from Merino rams' wool were ineffective either alone or in addition to fenceline ram exposure. Pre-isolation of ewes from rams was not required when novel rams were used to induce subsequent ovulation. Keywords: ram stimuli; induced ovulation; ewes