Morphological Evaluation of Ovary in Relation to Recovery, Quality of Oocytes and Steroid Production in Sheep

Abstract

The purpose of current study was to evaluate the effect of follicles, corpus luteum (CL) and steroid production (progesterone
and estradiol) on the morphology of sheep ovaries, with the view of in vitro recovery, quality, and maturation of oocytes. Fifty
ovarian pairs grouped into right, and left, CL bearing and non-CL -bearing ovaries were used in the current study. The weight,
length, width and thickness of ovaries were recorded. The follicles were classified into 3 groups small (>2mm), medium (2-4mm)
and large (>4mm) follicles. Oocytes were classified according to their morphology into 3 grades COCS (Compact cumulus oocyte
complexes), POCS (Partially invested with less than three layers of cumulus cells), DO (denuded oocyte). The concentration of
progesterone and estradiol 17β in the follicular fluid were estimated. The dimensions of ovaries between right and left ovaries
were not significantly different. However, the ovarian dimensions as well as their weight was significantly (P < 0.05) affected by
presence of CL, being higher in CL bearing ovary than that of non-CL bearing ovary. The average number of large follicles were
significantly (P < 0.05) increased in the right ovary (1.0±0.14) when compared to the left ovary (0.6±0.10). The recovered COCs
number was found to be significantly higher (P < 0.05) in the right than left ovaries (2.0±0.13; 1.2 ±0.09 respectively). A greater
number of vesicular follicles and aspirated COCS were found in non-CL bearing ovary (5.0 ±0.97;1.25±0.09 respectively) than in
CL bearing ovary (3.0±0.67;0.80±0.13 respectively). The CL-absent ovaries provide large numbers as well as high quality of COCs
when compared to CL-present ovaries and that CL-absent ovaries can be used to collect quality COCs for in vitro production of
sheep embryos.