title: In vitro developmental competence of bovine oocytes: Effect of corpus luteum and follicle size.
abstract: BACKGROUND
  Previous studies reported many discrepancies about the effects of corpus luteum (CL) and ovarian follicle size on the developmental competence of oocytes.
  
  
  OBJECTIVE
  The aim of this study was to investigate the effects of CL and different size of follicle on the developmental potential of bovine oocytes.
  
  
  METHODS
  After ovarian classification based on presence or absence of CL, sample follicles were placed in three groups according to their diameter; small (S; 3-6 mm), medium (M; 6-9 mm), and large (L; 10-20 mm). Collected oocytes in each group were subjected to the in vitro embryo production processes.
  
  
  RESULTS
  Results showed that, the percentages of blastocyst obtained from oocytes originating from small and medium follicles of ovaries bearing a CL (CL+S-oocytes and CL+M-oocytes, respectively) were lower (p<0.001) than those of small and medium follicles of ovaries not bearing a CL (CL-S-oocytes and CL-M-oocytes, respectively) (30.8% and 33.6% vs. 36.9% and 38.7% respectively). Although, the percentages of blastocyst obtained from CL-M-oocytes and CL-L-oocytes were greater (p< 0.001) than those of CL+S-oocytes and CL+M-oocytes. There were no significant differences in the percentages of blastocyst formation between controls (C-oocytes), CL-S-oocytes and CL+L-oocytes.
  
  
  CONCLUSIONS
  According to the results of this study, the negative effect of CL on the developmental competence of bovine oocyte depends on the follicle size. Therefore, oocytes originating from large grown follicles were not influenced by negative effects of CL as much as those originating from small and medium follicles did.
authors.affiliation: IVF and ET Laboratory, Department of Animal Sciences, Razi University, Kermanshah, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Karami Shabankareh
authors.affiliation: IVF and ET Laboratory, Department of Animal Sciences, Razi University, Kermanshah, Iran. ; Department of Animal Sciences, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.
authors.forename: Mohammad Hamed
authors.initials: MH
authors.lastname: Shahsavari
authors.affiliation: IVF and ET Laboratory, Department of Animal Sciences, Razi University, Kermanshah, Iran.
authors.forename: Hadi
authors.initials: H
authors.lastname: Hajarian
authors.affiliation: Department of Animal Sciences, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.
authors.forename: Gholamali
authors.initials: G
authors.lastname: Moghaddam
keywords: Bovine; Development; Oocyte.