Effect of Reproductive Status on Yield and in Vitro Maturation of Oocytes of Egyptian Sheep

Abstract

The current study investigated the effect of breeding season and presence of corpora lutea (CLs) on the ovaries with, ovarian characteristics, and yield, quality and oocyte recovery rate in sheep. Also, the effect of addition of sheep serum (SS) and bovine serum albumin (BSA) to maturation medium of sheep oocytes during breeding and non-breeding season was studied. Ovaries were collected during breeding and non-breeding seasons from slaughterhouses. Ovaries were classified with or without CLs during both seasons. Oocytes were collected by slicing and their yield, category and recovery rate were determined. Only compact oocytes (COCs) were in vitro matured as affected by breeding vs. non-breeding season and addition of 10% SS vs. BSA. Results show that only ovarian weight was higher (P<0.05) in breeding than in non-breeding season and with CL-ovaries than without CLs. Ovaries were longer and thicker in breed in than in non-breeding season. CL-ovaries during breeding season showed the highest ovarian characteristics. Number of all visible follicles/ovary tended to be higher (P<0.05) in breeding than in non-breeding season and of ovaries with than without CLs (P≥0.05). Oocyte yield/ovary was greater (P<0.05) by 41.7% in breeding than in non-breeding season. Oocyte yield was insignificantly greater on ovaries with CLs than those without CLs. Oocyte recovery rate was insignificantly higher in breeding and on ovaries with CLs than in non-breeding season and on those without CLs. Number/ovary and percentage of COCs were higher, while number/ovary were lower in breeding than in non-breeding season (P<0.05). Number and percentage of all categories were higher for oocytes recovered from ovaries with than without CLs. Percentage of oocytes at M-I stage was slightly higher in non-breeding than in breeding season. Percentage of oocytes at M-II showed an opposite trend, reflecting insignificantly higher maturation rate in breeding than in non-breeding season. Percentage of oocytes at M-I and M-II stages was insignificantly higher in BSA than in SS-medium. Oocyte maturation rate with SS than with BSA in breeding and non-breeding season. In conclusion, sheep oocytes were available to be harvested during non-breeding season from slaughtered ewes with acceptable yield, quality and the maturation rate in vitro by addition sheep serum (10%) to maturation medium.