Effect of Age and Hormonal Stimulation on Development of Beef Follicles and Oocytes During Ultrasound-Guided Transvaginal Follicular Aspiration

The effect of age and exogenous hormonal stimulation on development of beef (Murray Grey×Brahman) follicles and oocytes were investigated during ultrasound-guided transvaginal follicular aspiration (TVFA).Results showed:mean number of follicles (≥2 mm) and number of follicles ＞10 mm in diameter were higher in heifers and pluriparous than those in older beefs (P＜0.01);mean number of oocytes and COC were higher in the heifers and pluriparous than those in the older beefs (P＜0.05).Among heifers,pluriparous and older beefs,percentage of Ⅰ and Ⅱ grade oocytes were successively decrease,and percentage of Ⅲ and Ⅳ grade ones were opposite (P＜0.05).Ⅱ grade oocytes were more than others in the heifers and pluriparous,and Ⅲ grade oocytes were more than others in the older beefs.After pluriparous or older beefs stimulated by FSH,mean number of follicles was not different among different groups (P＞0.05),but number of follicles ＞6 mm in diameter was increased and 2-5 mm in diameter was accordingly decreased (P＜0.05),percentage of Ⅱ grade oocytes was increased,and percentage of denuded and degenerated oocytes was deceased.Mean number of follicles,oocytes and COC in the heifers and pluriparous were lower at the aspiration of estrus day than that at the other aspirations.In conclusion,oocytes can be obtained from live beefs,age can affect development of beef follicles and oocytes that could base on different physiological state,and appropriate exogenous hormonal stimulation can improve follicular development.