Impact of follicular aspiration on folliculogenesis as influenced by dietary energy and stage of lactation

Prolonged dietary energy restriction has been shown to influence the secretion of ovarian hormones and follicular development. Energy balance affects the ability of the cow to support a functional reproductive system during early lactation. Follicular aspiration is a tool that can be used to assess the impact of dietary energy and stage of lactation on follicle development in dairy cattle. Follicular aspiration was conducted twice weekly from d 30 to 100 postpartum in cows fed either 104 or 80% of NRC energy requirements. Oocyte numbers recovered increased linearly from d 30 to 100 postpartum. Cows on high energy diets produced more high quality oocytes, but also produced more poor quality oocytes than cows fed the lower energy diet. Follicles < 5 mm predominated throughout. Cows in early (d 28) and mid (d 117) lactation were used to assess stage of lactation effects on serum and follicular fluid hormones, and quality of oocytes recovered by follicular aspiration procedures for 10 wk. Serum IGF-1 decreased in early lactation cows, but increased in midlactation cows. Follicular fluid progesterone in early lactation cows decreased from 275 to 235 ng/ml, whereas in midlactation cows it increased from 65 to 550 ng/ml at aspiration wk 10. The percentage of high quality ova was higher in early lactation cows (11%) than midlactation cows (6%), but fell to 1% by aspiration wk 7 and increased to 10% by wk 10, whereas percentage of high quality ova in midlactation cows steadily declined to 2% by wk 10. Milk yield and energy balance affect patterns of folliculogenesis in lactating dairy cows.