Increases in ovulation rate and gonadotrophin concentration in goats and Merino sheep after treatment with bovine follicular fluid

Abstract

In this study we treated mixed-breed goat does and Merino ewes with bovine follicular fluid (bFF), a rich source of the ovarian hormone inhibin, to test the hypothesis that treatment will increase ovulation rate. Twenty-two goat does of mixed breeding (non-dairy) and 24 Merino ewes were each divided into two equal groups and injected subcutaneously every 8 h with 2 ml of either saline or charcoal-extracted bFF for the final 4 days of the luteal phase. Luteolysis was induced 8 h after the last injection with a synthetic protaglandin. The concentrations of follicle-stimulating hormone (FSH) and luteinising hormone (LH) in blood plasma were monitored daily during treatment and then every 8 h for 3 days after luteolysis. Ovulation rate was determined by laparoscopy on Day 11 of the subsequent cycle. During treatment with bFF the plasma concentration of FSH in both the ewes and the does was significantly ( P<0.01) reduced; however, the plasma concentration of LH in the does was not reduced by bFF treatment. When the treatment with bFF was stopped, FSH concentrations increased three-fold over normal control levels. The LH concentrations of both the control and the bFF-treated does increased ( P<0.01) after withdrawal of treatment, but the maximum value of the bFF-treated does was two-fold higher than that of the control does. Ovulation rate significantly increased by 40% from 1.17 to 1.64 in the ewes ( P<0.05), and by 29% from 1.55 to 2.00 in the does ( P<0.05). The results from this study extend on other reports on the effect of high doses of follicular fluid in highly fecund breeds of sheep by showing that ovulation rate can be increased with low doses in goats and low fecundity Merino sheep.