Effect of Physico-Biochemical Characteristics of Follicles on Quality and In Vitro Maturation of Bubaline Oocytes

Abstract

The physico-biochemical properties of follicles and its plausible effect on quality and maturational competency of oocytes during the different breeding periods of the year was studied in buffaloes (Bubalus bubalis). Ovaries were collected from sexually mature buffaloes slaughtered at abattoir during high breeding (December-February; HB) and low breeding (April-July; LB) periods of the year. The surface antral follicles were categorized as small (SF; < 4 mm), medium (MF; 4-9 mm) and large (LF; >9 mm) follicles. The follicular fluid (FF) was aspirated from follicles of different categories and the recovered oocytes were assessed for their quality. The good quality oocytes were cultured in vitro to assess the maturational competency. The glucose (Glu), total proteins (TP) and triglycerides (Tgl) concentrations of FF were analysed and correlated with the oocyte quality and maturation capacity. Among the follicular categories, significantly (P<0.01) more percentage of good quality oocytes with high maturation rate was recovered from MFs and vice versa for oocytes from LFs in both the periods. The mean percentage of good quality oocytes and the mean percentage of oocytes that reached the MII stage was significantly (P<0.01) higher during HB than LB period. The Glu concentration increased as the follicle size increased, while the TP concentration remains similar in all follicular categories but the Tgl concentrations were significantly higher in SFs. In general, the concentrations of these three biochemical components, with significance to Tgl, were found to be increased in the FF during the LB period correlating with the deteriorated oocyte quality and developmental properties. This might mean that metabolic activities were less intensive resulting in lower consumption of these components by the follicular cells and oocytes during the LB than HB period leading to fall in fertility levels during the former period.