Growth and development of follicles in different phases of the oestrous cycle in cows in relation to the presence of the corpus luteum and an oestrogen-dominant follicle
Lazár, L.; Maracek, I.
Veterinarni Medicina 39(11): 653-661
1994
ISSN/ISBN: 0375-8427 PMID: 7817498 Document Number: 423699
Ovaries were obtained from cows slaughtered at an abattoir. The stage of the oestrous cycle at which slaughter was carried out was determined on morphological criteria of the corpus luteum, and by serum progesterone determinations. The 4 stages were days 1-4, 5-10, 11-17 and 18-20. Ovarian follicles were measured, and the follicles were classified as small (<4.9 mm), medium (5.0-9.9 mm) and large (>10 mm). Follicular fluid was aspirated from the 47 largest follicles. The highest number of follicles occurred in the follicular stage of the oestrous cycle (stage 4). The percentage of large follicles was 4.7, 3.9, 4.8 and 3.1 in the 4 stages respectively, and that of small follicles 78.7, 88.5, 84.8 and 93.4. The presence of a corpus luteum had a negative effect on the recruitment of small follicles at all stages of the oestrous cycle. The presence of a large, oestrogen-dominant follicle suppressed the presence of an additional large follicle and inhibited recruitment of small follicles, but had a positive effect on the number of medium and large follicles on the ipsilateral ovary.