Respuesta reproductiva de ovejas multíparas postparto y nulíparas a inyecciones de GnRH y prostaglandina F2α

Abstract

The objective was to compare the reproductive responses of postpartum multiparous and nulliparous ewes to GnRH and PGF2α injections. The ewes in G1 (n=14) were lactating, non-pregnant and with 68.21±13.48 days postpartum. The ewes in G2 (n=13) were lactating, non-pregnant and with 93.76±7.25 days postpartum. The ewes in G3 (n=14) were non-pregnant and non-lactating. Transrectal ultrasonography was carried out nine days apart to assess ovarian activity. Then, two GnRH injections were given nine days apart to ewes. An injection of PGF2α and a third injection of GnRH was administrated to ewes seven and nine days after the second injection of GnRH. The number of ewes bearing a corpus luteum was higher after the injections with GnRH (P≤0.05). Follicle population was higher (P≤0.05) in ewes from G1 than in ewes from G2 and G3. The diameter of the largest ovarian follicle was larger (P≤0.05) in G2 than in ewes from G1 and G3. Estrus presentation and pregnancy rate were not different among groups (P>0.05). In conclusion, two GnRH injections increased the incidence of corpus luteum and equalized estrus presentation and pregnancy rate after PFG2α injection in postpartum multiparous ewes compared to nulliparous ewes.