Effect of the Stage of Sexual Cycle, Harvesting Technique and Season on Follicular Dynamics and Oocyte Quality of Zebu Cattle under Sudano-Sahelian Climate

Abstract

This study was carried out at the Ngaoundere Slaughterhouse (Adamawa region, Cameroon) on 353 normal cyclic zebu cows to investigate the effects of the stage of sexual cycle, harvesting technique and season on follicular dynamics and quality of cumulus-oocyte complexes (COCs). The stages of the sexual cycle were divided into estrus, metestrus, diestrus and proestrus. The oocytes were retrieved using the following techniques: slicing, aspiration, puncture, aspiration followed by slicing and puncture followed by slicing and classified into grades I, II, III and IV. The results indicated that the follicular population was 27.26±1.95 follicles per cow. Oocytes recovery rate was 10.14±8.37 per cow. The oocyte quality index and oocytes grade I and II acceptable for in vitro embryo production (IVEP) were 2.35 and 58.28%, respectively. The stage of sexual cycle of cows has a significant effect (P < 0.05) on the large follicles (> 8 mm) but has no effect on the yield and oocytes quality. The rainy season offers a higher number of follicles and oocyte quality than the dry season. Slicing technique allows the best yield of oocyte acceptable for IVEP. The ascending hierarchical classification revealed that, to obtain the best rate of oocyte yield and quality, they should be retrieved in Gudali from the Vina by slicing or aspiration in the rainy season at estrus or metestrus stage, lower than 6 years old with a live weight of 368.53 kg, body condition score of 3 and ovaries weight > 5g with medium follicles (3 to 8 mm).