Follicular population and progesterone (P4) plasma concentrations in sheep under different synchronization protocols

Abstract

The effect of prostaglandin (PGF_2α) vs CIDR and eCG (equine corionic gonadotrophin) on dynamic of foUicular population and its relationship with P₄ plasma concentrations were investigated in cyclic ewes. Fourteen Bergamascia ewes were used, Group 1 was synchronized using two i.m. injections of PGF_2α, and Group 2 treated for 14 d with CIDR and 500IU of eCG at dispositive withdrawal on day 14. Ovarian foUicular dynamics were ultrasonically monitored. All ovarian follicles ≥ 2 mm were measured, and their relative locations were recorded on an ovarian map in order to follow the sequential development of each individual follicle. Blood samples for P₄determination were collected daily starting the day before the second injection of PGF_2α, (Gl) and from administration of eCG (G2) until day 10 after ovulation of the cycle. There were significant (P<0.001) differences in P₄ plasma concentrations among treatments. The CIDR + eCG (500 IU) treatment increased the recruitment of smaller follicles and the maximum diameter and growth rate of large follicles during the first wave.