INFLUENCE OF DRY AND RAINY SEASONS ON OOCYTE MATURATION AND IN VITRO EMBRYO PRODUCTION IN GOATS

Abstract

This study aimed to determine the influence of dry and rainy seasons on oocyte maturation and in vitro production (IVP) of embryos in goats. The ovaries of does in dry (October to March) and rainy season (April-September) were collected at a slaughterhouse and transported to the Laboratory of Biotechnical Reproduction of UFRPE. The cumulus oophorus complexes (COCs) were collected by the technique of slicing of the follicles from 2 to 6 mm in diameter, and selected based on morphologic classification. We used 12 replicates, in which the COCs were submitted to maturation, fertilization and in vitro culture. The cleavage rate was determined on day 3 (D-3) and embryos that developed to 8-16 cells (D-4), morulae (D-5) and blastocyst (D-8) stages after fertilization. The number of blastomeres was assessed with DAPI staining, and the determination of apoptotic blastomeres was performed by TUNEL assay. In the dry season, D-3 embryos and morulae development was lower than that obtained in the rainy season (P<0.05). However, no differences (P>0.05) were observed on oocyte maturation, fertilization, D-4 embryo yield and blastocyst development. Embryos produced during the dry season had a higher incidence of apoptosis on D- 3 and at the morulae stage (P<0.05). Under the conditions described in this study, the results suggest that the early stages of embryonic development suffer greater negative impact during the dry season in IVP protocols in goats. KEYWORDS: Apoptosis; cumulus oophorus complexes; IVF; oocyte development; TUNEL test.