Induction of cyclic ovarian activity in seasonally anoestrous ewes with exogenous GnRH

Anoestrous ewes (N = 3) were treated with a 500 ng GnRH pulse administered via a jugular cannula every 2 h for 40 to 80 days. Plasma concentrations and therefore presumed ovarian activity changed cyclically with each progestational cycle (n = 10) lasting 14.0--18.5 days. It is concluded that, by increasing the frequency of GnRH secretory episodes from an apparent endogenous level of one episode per 3.6 h to at least one every 2.0 h, cyclic ovarian activity can be restored to seasonally anoestrous sheep.