Effects of the gonadotropin dose on estrus and embryo production in Hamra and Ouled Djellal ewes

Abstract

The application of superovulation and embryo production techniques is essential for the conservation of sheep genetic resources. The objective of this study was to evaluate the effect of two doses of porcine follicle-stimulating hormone (pFSH) on the onset and duration of estrus, the ovarian response and the production of embryos in sheep of Ouled Djellal (OD) and Hamra (H) breeds. OD ewes (n = 15) and H ewes (n = 14) were synchronized by the insertion of vaginal sponges impregnated with 40 mg of fluorogestone acetate (FGA), and superovulated by the administration of 16 or 20 AU of pFSH during the last three days of progestagen treatment. On day seven after estrus and natural mating the embryos were collected by laparotomy. In OD ewes treated with 20 AU the onset of estrus occurred earlier than in those treated with 16 AU (22.1 ± 4.5 vs 25.0 ± 3.5, p < 0.05), and the duration of estrus was longer (34.0 ± 6.6 vs 40.0 ± 7.1, p < 0.05). In H ewes, the increase in the pFSH dose from 16 AU to 20 AU induced a decrease in embryo production: collection rate 72.2 vs. 47.1, p < 0.001; number of structures collected 5.9 ± 3.4 vs 3.6 ± 2.1, p < 0.05; number of embryos harvested 3.2 ± 1.9 vs 5.1 ± 2.6, p < 0.05; 1-and-2-grade embryos 4.3 ± 2.4 vs 2.1 ± 1.7, p < 0.01. On the other hand, in OD ewes treated with 20 AU the ovulation rate and embryo production were significantly improved: number of corpora lutea 6.9 ± 3.9 vs 10.4 ± 5.4, p < 0.05; number of embryos harvested 3.2 ± 2.0 vs 5.1 ± 2.3, p < 0.05; 1-and-2-grade embryos 2.2 ± 1.6 vs 4.3 ± 1.7, p < 0.05. The results indicate that the ovulatory response, estrus, and embryo production are influenced by the dose of pFSH and the breed.