Factors affecting follicular population, oocyte yield and quality in camels ( Camelus dromedarius) ovary with special reference to maturation time in vitro

Abstract

Three experiments were conducted to study a series of factors affecting in vitro reproductive parameters in camels. In Experiment 1, the effect of season and presence of a corpus luteum (CL) on ovarian follicular populations, oocyte yield and quality was studied using a total of 252 and 208 ovaries collected during the breeding and non-breeding season, respectively. Small, medium, large and the total number of ovarian follicles, oocyte yield and quality were measured. In Experiment 2, the effect of methods of oocyte retrieval and needle gauge on oocyte yield and quality was evaluated with oocytes recovered using slicing and aspiration with 18-, 19- or 20-gauge needle. Oocytes were evaluated microscopically and classified into three categories. The objective of Experiment 3 was to identify the optimum time for oocyte maturation in the dromedary camel. Oocytes were cultured in CR1aa medium at 38.5°C under 5% CO 2 for 24, 32, 36, 48 and 72 h. Maturation was calculated as the percentage of cumulus expansion and oocytes reaching metaphase II (MII). The number of small, medium, large and the total number of ovarian follicles were higher ( P<0.01) during the breeding than non-breeding season. The recovery of total number of oocytes and Category I oocytes were also greater ( P<0.01) during the breeding season. Ovaries without a CL possessed significantly ( P<0.01) more ovarian follicles and more ( P<0.05) small and large follicles. The total number of oocytes and Category I oocytes were also greater ( P<0.01) in ovaries without CL. Slicing of camel ovaries increased ( P<0.01) the yield of oocytes as compared to aspiration. The aspiration of follicles using a 20-gauge needle had greater yields of the total number of oocytes and Category I oocytes than when using 19- ( P<0.05) and 18-gauge needle ( P<0.01). The culture of camel oocytes for 36 h produced higher ( P<0.01) percentages of cumulus expansion and oocytes at MII. Increasing culture times up to 48 or 72 h increased ( P<0.01) the percentage of degenerated oocytes. In conclusion, the growth and development of ovarian follicles in the camel as well as yields of Category I oocyte were greater during the breeding season. Slicing or aspirations using a 20-gauge needle yielded greater numbers of total and Category I oocytes. Finally, maturation of oocytes in CR1aa medium for 36 h produced higher percentages of cumulus expansion and oocytes at MII stage.