Effect of season and gonadotrophin preparation on superovulatory response and embryo quality in Portuguese Black Merinos

Abstract

The aim of the study was to assess the effect of season (Spring or Fall) and stimulation with either ovine FSH (Ovagen®) (oFSH) or porcine FSH (Pluset®) (pFSH) on the superovulatory response and embryo quality in Portuguese Black Merino ewes. Ewes were synchronized with intravaginal sponges containing FGA (fluorogestone acetate) and subjected to laparoscopic intrauterine insemination and natural mating. Ovary examination and embryo recoveries were carried out with the aid of laparotomy on day 7 following sponge withdrawal and the number of CL's, unfertilized oocytes, empty zona pellucida, total number of embryos and total number of freezable embryos recorded. Fertilization and embryo freezability rates, efficacy of flushing, and embryo recovery rates were also determined. No significant differences were recorded in the number of CL's, total number of embryos and freezable embryos between seasons. Higher (p < 0.05) flushing efficiency (80% versus 60%) and embryo recovery rates (80% versus 50%) (p < 0.01), were obtained during Spring, with embryo freezability being higher in the Fall (90.5% versus 64.4%). No differences were recorded in the ovarian response (number of CL's) and the superovulatory response (≥4 CL's) for ewes stimulated in Spring with either oFSH or pFSH. The total number of embryos, flushing efficiency and embryo recovery rate was higher (p < 0.05) in the oFSH-treated ewes. From these trials it can be concluded that MOET programs can be successfully incorporated in Portuguese Black Merino ewes, either in Spring or Fall—despite a higher proportion of freezable embryos being obtained in the Fall (90.5% versus 66.4%). More acceptable results in terms of the total number of embryos (7.2 versus 3.1), flushing efficiency and embryo recovery rate (80% versus 30%), were obtained with oFSH than the pFSH preparation. Data on recovery of freezable embryos may be used as an indicator of the number of donors needed in this specified breed.