Estrus syncrhonization in ewes with prostaglandins at dif-ferent days post CIDR insertion Estrus syncrhonization with prostaglandins at different days

Abstract

Objective: To evaluate the effect of PGF_2α application on days 0, 3 and 6 of the synchronized luteal phase on reproductive perfomance and its effect on progesterone concentrations of multiparous ewes.

Design/methodology/approach: The experimental design was a completely randomized. Seventy-five ewes synchronized with CIDR for 6 days and 250 UI of eCG were used at device removal. The ewes were randomly distributed in three treatments in relation to the days of application of PGF_2α (125 μg sodium cloprostenol): in the first group of ewes, PGF_2α was applied at the time of insertion of the CIDR (D0, n=25); in the second group PGF_2α was applied on day three of insertion of the CIDR (D3, n=25) and in the third group it was applied on day six, at the time of the withdrawal of the CIDR (D3, n=25). The presentation of estrus and the gestation rate were analyzed through the c² test. The onset of estrus and prolificacy by a Tukey analysis of variance and comparison of means. The concentration of P₄ was carried out using the PROC MIXED procedure, which included fixed effects of treatment and day, and interaction of both.

Results: Presentation and onset of estrus were different (P<0.05) between treatments due to the effect of the interval in the days of PGF_2α application. The P₄ concentrations in blood serum showed differences during the synchronized luteal phase (D0: 4.8 ng mL^-1; D3: 6.0 ng mL^-1, D6: 8.8 ng/mL^-1). However, no differences were found in gestation rate and prolificacy due to main effects.