Abstract

The aim of the present study was to establish whether ovulation and normal corpus luteum function could be induced in anoestrous ewes by supplementing the endogenous level of luteinizing hormone (LH) and whether cyclical ovarian activity could be induced and maintained in seasonally anoestrous ewes by an unvarying long-term intravenous pulse regime of gonadotrophic releasing hormone (GnRH), 500 ng once per 2 h or 43-80 days. The results demonstrated that a normal ovulation can be induced in anoestrous ewes with LH alone and that the aforementioned GnRH regime was successful in inducing cyclical progesterone activity. These findings suggest that normal breeding activity may be restored to anoestrous ewes when the frequency of hypothalamic GnRH is increased from an apparent endogenous level of secretory episode per 3.5 h to 1 episode per 2 h.

XJ, Duff, SN McCutcheon, and MF McDonald

Proceedings of the New Zealand Society of Animal Production, Volume 42, , 15-18, 1982