Effect of the stage of estrous cycle on follicular population, oocyte yield and quality, and biochemical composition of serum and follicular fluid in Anatolian water buffalo

This study was designed to investigate the effects that the different stages of the estrous cycle had on the number of surface ovarian follicles and oocyte yield and quality of Anatolian water buffalo during peak breeding season. Assessments were made on the basis of ovarian morphology, serum and follicular fluid concentrations of variety of biochemical parameters. Following slaughter, blood samples were collected from each animal. The stage of estrous cycle was classified as either the luteal or follicular phase, and surface ovarian follicles were classified as small, medium, or large. The follicular fluid was aspirated, and oocytes were evaluated microscopically for classification into four categories. No statistical differences (p > 0.05) were observed regarding the total number of follicles or quality of oocytes relative to the stage of the estrous cycle. Serum high-density lipoprotein cholesterol (HDL), alkaline phosphatase (ALP) and progesterone (P4) concentrations were significantly higher in the luteal phase than in the follicular phase (P < 0.05). Significant correlations were observed in the luteal phase between the total number of oocytes and cholesterol (Cho), HDL, sodium (Na), chloride (Cl); A-quality oocytes and Na, Cl, Mg; C-quality oocytes and Cho, HDL, and Mg in follicular fluid. These results offer new information concerning Anatolian water buffalo reproductive physiology, which may be useful for improving oocyte quality in buffalo. This is the first study to describe the number of ovarian follicles, oocyte yield and quality, and a variety of biochemical parameters in the serum and follicular fluid of Anatolian water buffalo during peak breeding season in Turkey.