Effect of Cumulus Cells on In Vitro Fertilization of Bovine Oocytes

Abstract

Bovine follicular oocytes (n=265) collected from abattoir ovaries were matured for 24 hours in modified Menezo's medium (MMM) supplemented with Na-pyruvat, glucose, FSH and oestrus cow serum (ECS). After maturation, oocytes were randomly divided into three groups. One group of oocytes (Group 1) was denuded from cumulus cells prior to fertilization and another group of oocytes (Group 2) was denuded 20 hours after fertilization. In the third group, oocytes were remained with cumulus cells intact (Control group). All of the oocytes were fertilized with frozen-thawed bull spermatozoa treated with swim-up procedure in a modified MenezoÕs medium supplemented with Na-pyruvat, HEPES, BSA, essential and non-essential amino acid solutions and vitamin solutions. Modified Tyrode-lactate medium supplemented with heparin, Na-pyruvat, BSA and PHE was used for fertilization medium. At the end of the maturation and fertilization in vitro, presumptive zygotes were transferred to the culture medium (modified MenezoÕs medium) and cultured for 7 days. After culture all of the embryos were fixed with 3:1 ethanol: acetic acid for 24 hours and stained with aceto-orcein for microscopic evaluation. Of the 80 oocytes in Group 1, 45 were fertilized (56.25 %). Embryos reached to morula and blastocyst stages were 8 (17.78 %) and 3 (6.67 %) respectively. In Group 2, of the 89 oocytes, 55 were fertilized (61.80 %). Embryos reached to morula and blastocyst stages were 8 (14.55 %) and 3 (5.45 %) respectively. In control group (n=96), 49 oocytes were fertilized (51.04 %). Embryos reached to morula and blastocyst stages were 12 (24.49 %) and 9 (18.37 %) respectively.