الفهرس 
Seasonality of reproduction
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
This study was carried out at IVF laboratory, International Livestock Management Training Center, Sakha, Kafr El-Shiekh Governorate belonging Animal Production Research Institute (APRI), Agricultural Research Center, Ministry of Agriculture, Egypt, in cooperation with Department of Animal Production, Faculty of Agriculture, Tanta University, during January 2016 until September 2017. Ovaries collection: Ovaries from female Barki were weekly collected during September-December (breeding season) and during March-July (non-breeding season) from private slaughterhouses in Borg El-Arab, Alexandria Province, located at distance approximately 225 km from the laboratory. The ovaries were collected within 15-30 minutes post slaughter and placed in punctured plastic bag and placed immediately after slaughtering into thermos in saline solution (0.9% NaCl) supplemented with antibiotics (100 IU penicillin and 100 μg streptomycin/ml) at 28°С. Thereafter, all collected ovaries were transported to the laboratory within 3 h Ovarian assessment: In the laboratory, the excess tissue from the ovarian stalk was cut from the (right or left) ovary for each donors. Ovaries washed tow times with warmed (28oC) phosphate buffer saline (PBS) supplemented with antibiotics (100 IU penicillin and 100 μg streptomycin/ml) to remove adhering clotted blood. Then all ovaries were quickly washed one time with ethanol (70%) to remove any contamination on the surface of the ovaries. Ovarian characteristics: After removal of the extraneous tissues, each ovary was classified with or without corpora lutea (CLs) and weighed using an electric balance in different season. Ovarian measurements, including length, thickness and width were measured using caliper. Oocyte collection: All visible follicles on the ovarian surface were counted, and oocytes were collected by slicing. The oocyte yield from each ovary and donor was recorded and the number of oocyte/ovary was calculated. The recovery rate was determined as percentage of oocyte in proportional to each of the total vesicular follicles present on the ovarian surface of each case using the following formula: Recovery rate (%) = (Number of recovered oocyte/ number of follicles) x 100. Oocyte categories: After collection, oocyte were washed three times in harvesting medium, thereafter oocyte were counted and then each oocyte were evaluated under stereomicroscopy and classified into four categories based on their cumulus investment as follows: compact oocytes with five or more layers of complete cumulus cells, partial oocytes with cumulus cells present either incompletely surrounding the oocyte, denuded oocytes without cumulus cells and covered by zona pellucida, and Shrunken or degenerated oocytes with ooplasm shrunken away from the zona pellucida or not evenly filling the zona ooplasm looks degenerated with fragment empty zona pellucida (Madison et al., 1992). Maturation medium (TCM-199) was supplemented with 10% sheep serum (SS) or 6 mg/ml bovine serum albumin (BSA, 160096, Mp) to define the optimal group affecting maturation rates of sheep oocytes in breeding and non-breeding seasons. Blood samples were taken from adult ewes without reproductive history, and then serum was collected and stored at -20oC.