Follicular dynamics and concentrations of steroids and gonadotropins in lactating cows and nulliparous heifers.
Differences in follicular development and circulating hormone concentrations, between lactating cows and nulliparous heifers, that may relate to differences in fertility between the groups, were examined. Multiparous, cyclic, lactating Holstein cows (n=19) and cyclic heifers (n=20) were examined in the winter, during one estrous cycle. The examinations included ultrasound monitoring and daily blood sampling. Distributions of two-wave and three-wave cycles were similar in the two groups: 79 and 21% in cows, 70 and 30% in heifers, respectively. Cycle lengths were shorter by 2.6 days in heifers than in cows, and in two-wave than in three-wave cycles. The ovulatory follicle was smaller in heifers than in cows (13.0+/-0.3 mm versus 16.5+/-0.05 mm). The greater numbers of large follicles in cows than in heifers corresponded well to the higher concentrations of FSH in cows. The duration of dominance of the ovulatory follicle tended to be longer in cows than in heifers. Estradiol concentrations around estrus and the preovulatory LH surge were higher in heifers than in cows (20 versus 9 ng/ml). Progesterone concentrations were higher in heifers than in cows from Day 3 to Day 16 of the cycle. Circulating progesterone did not differ between two-wave and three-wave cycles. The results revealed differences in ovarian follicular dynamics, and in plasma concentrations of steroids and gonadotropins; these may account for the differences in fertility between nulliparous heifers and multiparous lactating cows.
Department of Animal Science, Faculty of Agriculture, The Hebrew University, Rehovot 76100, Israel. wolf@agri.huji.ac.il
David
D
Wolfenson
Gil
G
Inbar
Zvi
Z
Roth
Moshe
M
Kaim
Amir
A
Bloch
Ruth
R
Braw-Tal
D000818:Animals; D002417:Cattle / Q000097:blood*; D004958:Estradiol / Q000097:blood; D030762:Estrous Cycle; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006062:Gonadotropins / Q000097:blood*; D007774:Lactation; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000502:physiology*; D010060:Ovulation; D010298:Parity; D011374:Progesterone / Q000097:blood; D012621:Seasons; D013256:Steroids / Q000097:blood*; D013997:Time Factors; D014463:Ultrasonography
D006062:Gonadotropins; D013256:Steroids; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone