Follicular and oocyte maturation in cows treated for superovulation.
The maturational stage of oocytes and their follicles was assessed at 24/26 h after the preovulatory luteinizing hormone (LH) peak by means of morphological criteria. Follicles were obtained from cows treated for superovulation (PMSG/PG) with additional anti-PMSG to neutralize the residual PMSG. Follicular fluid was also recovered and analyzed for progesterone and estradiol levels. Seventy-two percent of the oocytes were at the Metaphase II (M(II)) stage of meiosis, whereas only 28% of the follicular walls were at the proper maturational stage; assessed on morphological characteristics, 78% of the follicles were progesterone-dominated. Earlier maturational stages of oocytes and follicles were also present, including those that are restricted to periods shortly after the LH peak in the normally cyclic cow. It is concluded that upon treatment for superovulation not all oocytes and follicles mature synchronously, and that not all oocytes mature in harmony with their follicles.
de Loos
F A
FA
Department of Herd Health and Reproduction, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 7, 3584 CT Utrecht, The Netherlands.
Bevers
M M
MM
Dieleman
S J
SJ
Kruip
T A
TA