Superovulation of Merino ewes with an ovine pituitary follicle stimulating hormone extract.

In order to investigate the effectiveness of ovine FSH as a superovulatory gonadotrophin in sheep, three batches (oFSH-1, oFSH-2 and oFSH-3) of crude follicle stimulating hormone (FSH) extracts were prepared from ovine pituitaries by protein fractionation. The extracts were characterized in radioimmunoassays (RIA), radioreceptor assays (RRA) and bioassays. A FSH:LH (luteinizing hormone) ratio of 1:0.71 and 1:0.18 was calculated from oFSH-1 in RIA and RRA respectively. oFSH-1 was more potent than NIH-oFSH-S12 in RRA, with a potency ratio of 1:0.65 calculated at 50% binding. In mouse bioassay, oFSH-2 was effective in inducing folliculogenesis. The potency of oFSH-3 as an ovarian stimulatory hormone was tested in a field trial on sheep. Thirty-one mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 6, 12 or 24 mg doses of oFSH-3 were injected twice daily for 3 days (n = 10 or 11). Each ewe was inseminated in the uterus with fresh semen 24 h after pessary withdrawal. Ova or embryos were recovered by mid-ventral laparotomy 6 or 7 days after pessary withdrawal. The dose of oFSH-3 had a significant effect on the ovulatory response (P less than 0.01); the mean ovulation rates were 1.5 +/- 0.2, 12.6 +/- 2.8 and 13.1 +/- 2.9 following injection with 6, 12 or 24 mg of the gonadotrophin respectively. The dose of the gonadotrophin injected had no effect on the mean percentages of ova recovered or fertilized. The overall ova recovery and fertilization rates (%) were 67.8 +/- 6.4 and 92.2 +/- 5.1 respectively. (ABSTRACT TRUNCATED AT 250 WORDS)