Abstract

A CIDR was inserted into 72 ewes which were either early in the cycle (E; days 1-3), at mid cycle (M; days 7-9) or late in the cycle (L; days 13-15). Half of the ewes received either 0 or 300 IU of pregnant mares' serum gonadotrophin (PMSF) at the start of superovulation treatment. M ewes had two thirds as many ovarian surface follicles >1.5 mm diameter compared to E and L ewes (8.8 vs 13.6 vs 13.0; P<0.001). M ewes had approximately two thirds as many ovulations present 8 days later compared to E and L ewes (5.1 vs 7.7 vs 7.7; P<0.05). For ewes receiving 300 IU of PMSG as well as FSH, there was a significant regression of follicle number on ovulation rate (b=0.73

RW, McAnulty, AS Familton, and AR Sykes

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 95-96, 1991