EFFECTS OF FGA AND PMSG ON FOLLICULAR-GROWTH AND LH-SECRETION IN SUFFOLK EWES

The effects of fluorogestone acetate (FGA) and/or pregnant mare serum gonadotrophin (PMSG) on follicular growth and LH secretion in cyclic e wes were determined. Suffolk ewes (n = 40), previously synchronized wi th cloprostenol were divided into 4 experimental groups (n = 10 ewes p er group). Group I served as the control, while groups II, III and IV received FGA, PMSG, FGA and PMSG respectively. Four ewes of each group underwent daily laparascopy for 17 d. All the ovarian follicles great er than or equal to 2 mm were measured, and their relative locations w ere recorded on an ovarian map in order to follow the sequential devel opment of each individual follicle. Comparisons were made of the mean day of emergence and the mean number of small, medium and large follic les, the atresia rate and the ovulation rate. For each group, 3 waves of follicular growth and atresia were observed during the cycle. Durin g luteal phase, FGA treatment accelerated the mechanisms of follicular growth but reduced the number of large follicles and increased the at resia rate. In the follicular phase, FGA treatment was detrimental to both the number of large follicles and the ovulation rate. By contrast , PMSG enhanced recruitment of small follicles and the ovulation rate. Serial blood samples were collected during the luteal and follicular phases to study LH secretion. None of the treatments had any effect on LH secretion patterns.