In vitro PRODUCTION OF NELORE BOVINE EMBRYOS ORIGINATED FROM OOCYTES FROM OVARIES WITH AND WITHOUT CORPUS LUTEUM

Abstract

This study aimed to compare the quality and quantity of oocytes aspirated from ovaries containing or not corpus luteum (CL), the development of embryos, pregnancy rate and sex ratio among embryos after IVP in Nellore cows. Follicular aspirations were performed in both ovaries of 219 cows in 250 sections, and equally divided into five groups: G1 = pregnant, G2 = not pregnant, with CL and submitted to hormonal therapy with progestin+BE+PGF_2µ; G3 = not pregnant, without CL and with the same treatment of G2; G4 = not pregnant, with the presence of CL and no treatment; G5 = not pregnant, without the presence of CL and no treatment. The statistical analysis was performed with analysis of variance (ANOVA) and Tukey Test was applied to compare means at 5% significance level, by SISVAR program. For the comparison of sex ratio within and between groups, the multiple comparison test of proportions was used. The G4 produced higher mean of total aspirated oocytes than G2 and G3. Comparing the three groups with CL, G4 showed higher number of oocytes than G1 and G2 in both ovaries. The G2 presented more viable oocytes than G1 in the CL-containing ovary. The ovaries without CL showed better production in pregnant cows despite of viable oocytes (p<0.05), and similar embryo production (p>0.05) when compared with ovaries presenting CL. Oocytes obtained from ovaries with CL resulted in better rates of embryo production. Pregnancy rates and sex ratio were similar among groups (p>0.05). The P₄ concentration was different between groups, but it did not influence any variable. The use of hormonal treatment did not improve the results of any variable. Therefore, choosing Nellore donors for IVP programs depends on knowing each animal individually along the sections of OPU.KEYWORDS: animal reproduction; follicular aspiration; serum progesterone