Ovarian follicular activity and hormonal profile during estrous cycle in cows: the development of 2 versus 3 waves
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Ovarian follicular activity and hormonal profile during estrous cycle in cows: the development of 2 versus 3 waves Wael MB Noseir* Address: Department of Theriogenology, Faculty of Veterinary Medicine, Alexandria University, Egypt Email: Wael MB Noseir* - [email protected] * Corresponding author
Published: 21 June 2003 Reproductive Biology and Endocrinology 2003, 1:50
Received: 06 May 2003 Accepted: 21 June 2003
This article is available from: http://www.RBEj.com/content/1/1/50 © 2003 Noseir; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.
Abstract Most estrous cycles in cows consist of 2 or 3 waves of follicular activity. Waves of ovarian follicular development comprise the growth of dominant follicles some of which become ovulatory and the others are anovulatory. Ovarian follicular activity in cows during estrous cycle was studied with a special reference to follicular waves and the circulating concentrations of estradiol and progesterone. Transrectal ultrasound examination was carried out during 14 interovulatory intervals in 7 cows. Ovarian follicular activity was recorded together with assessment of serum estradiol and progesterone concentrations. Three-wave versus two-wave interovulatory intervals was observed in 71.4% of cows. The 3-wave interovulatory intervals differed from 2-wave intervals in: 1) earlier emergence of the dominant follicles, 2) longer in length, and 3) shorter interval from emergence to ovulation. There was a progressive increase in follicular size and estradiol production during growth phase of each wave. A drop in estradiol concentration was observed during the static phase of dominant anovulatory follicles. The size of the ovulatory follicle was always greater and produced higher estradiol compared with the anovulatory follicle. In conclusion, there was a predominance of 3-wave follicular activity that was associated with an increase in length of interovulatory intervals. A dominant anovulatory follicle during its static phase may initiate the emergence of a subsequent wave. Follicular size and estradiol concentration may have an important role in controlling follicular development and in determining whether an estrous cycle will have 2 or 3-waves.
Background Ovarian follicular growth in cows occurs in waves. A wave of follicular growth involves the synchronous development of a group of follicles, one of which become dominant and achieves the greatest diameter suppressing the growth of the subordinate smaller follicles [1]. Transrectal ultrasonic imaging of ovarian follicles reveals that most estrous cycles in cows have two [2] or three [3] follicular waves. A retrospectively identified dominant follicle, its line of development was studied from the start of its growth till achieved the greatest diameter and was recog-
nized as a dominant follicle, grew linearly for
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