Bovine corpus luteum affects embryo developmental competence and production

Abstract

This study was conducted with the aim to determine the effect of bovine corpus luteum on in vitro embryo production. Immature cumulus–oocyte complexes (COCs) were aspirated from abattoir ovaries from cows with (ipsilateral; CL+) and without (contralateral; CL-) corpus luteum (CL), and from cows without CL in any of the ovaries. The experiment was completed within 12 replicates (100 ovaries per group). COCs were cultured in maturation medium (TCM-199 supplemented with 10% fetal bovine serum, 100 µg/ml sodium pyruvate, 0.75 mg/ml L-glutamine, 4 µg/ml FSH-p, 2 µM cysteamine and 250 µg/ml gentamicin) followed by in vitro fertilization (hepes synthetic oviductal fluid medium supplemented with 10 µg/ml heparin) and in vitro culture (citrate synthetic oviductal fluid medium). On day 7 after in vitro fertilization the embryos were evaluated and classified into morulae (M), early blastocysts (EB), blastocysts (B), expanded blastocysts (ExB) and hatched blastocysts (HB), and the embryos with better quality were recorded. Data were analyzed by logistic regression and general linear model of the SAS, and means compared by least-squares means method. Results of cleavage, embryo rate at day 7, and rates of M + EB, B, ExB and HB are shown in Table 1. The number of embryos per ovary was greater (P < 0.01) in CL+ (1.16 ± 0.11) than in CL- (0.45 ± 0.15) and C (0.55 ± 0.15). Also, the number of embryos per cultured oocyte was significantly greater in CL + than in CL- and C (0.27 ± 0.02 vs 0.14 ± 0.03 and 0.15 ± 0.03 respectively, P < 0.01). The results of this study reveal that the presence of the corpus luteum in the ovary at the time of the oocytes recovery affects the developmental capacity of the bovine embryos, and such influence probably occur through intraovarian interactions.