Pattern of growth of dominant follicles during the oestrous cycle of heifers

Abstract

Ovarian follicular development was studied in 13 heifers by daily ultrasound examination during 2 complete and consecutive natural oestrous cycles. In 21 cycles (81%) 3 dominant follicles were identified, in 4 cycles (15%) 2 and in the remaining cycle 1 (4%). Consistently, the first dominant follicle was detected on average on Day 4, reached a maximum size on Day 6, went through a period of relative stability between Days 6 and 10, then began to decrease in size and was undetectable by Day 15. The second dominant follicle was detected by Day 12, reached maximum size on Day 16 (or 19 in the 4 cycles in which the 2nd dominant follicle was the ovulatory follicle) and was undetectable by Day 19. The 3rd (ovulatory) follicle was identified on average by Day 16 (range Days 10 to 19) and maximum size was reached on Day 21. The ovulatory follicles were larger (P less than 0.05) than the previous ones and the stage of the cycle at which maximum size was reached was significantly different for each dominant follicle (P less than 0.05). The analysis of the rates of growth and atresia suggest that the rate of growth is slowest during mid-cycle. The number of dominant follicles that developed in the ovary ipsilateral to the corpus luteum was greater (P less than 0.05) than in the contralateral ovary.

A simple mathematical model of the bovine estrous cycle: Follicle development and endocrine interactions

“…Serum P4 concentration is near to zero around estrus and high during the luteal phase, with average peak levels ranging from 4.1-9.9 ng/ml [4,17,23,38,71]. A high correlation between CL diameter and P4 output was reported in [58,64,81]. However, Adams [4] found a correlation between CL size and P4 serum levels in the early luteal phase only, which could be due to changes in CL vascularity during the cycle, resulting in changes in P4 releasing capacity [46,50].…”

Parturition to resumption of ovarian cyclicity: comparative aspects of beef and dairy cows

“…Gonadotrophin-dependent follicle growth in cattle occurs in waves (Rajakoski, 1960;Matton et al, 1981;Ireland and Roche, 1987;Savio et al, 1988;Sirois and Fortune, 1988). Each wave of growth involves emergence, selection and dominance followed by either atresia or ovulation.…”

“…Normal follicle waves have an inherent lifespan of 7 to 10 days' duration from the time of emergence of a wave until emergence of the next wave (indicating either ovulation or physiological atresia of the dominant follicle). In cyclic heifers during the normal 21-day oestrous cycle (range 18 to 24 days), there are normally three waves (sometimes two waves and rarely one or four waves; Savio et al, 1988;Murphy et al, 1991;Forde et al, 2011). Pregnancy During pregnancy, follicular growth continues during the first two trimesters (Ginther et al, 1989 and1996) at regular 7 to 10-day intervals.…”

Follicular dynamic and ovulation in cattle – a review

“…Waves of growth can be observed during the prepubertal period EVANS et al, 1994;MELVIN et al, 1999), in pregnant cattle , in postpartum periods (MURPHY et al, 1990) and during oestrous cycles (ROCHE et al, 1999). During one interovulatory interval two KNOPF et al, 1989;RAJAMAHENDRAN and TAYLOR, 1991;AHMAD et al, 1997, BURKE et al, 2000BELLMANN 2001), three (SAVIO et al, 1988;SIROIS and FORTUNE, 1988;AHMAD et al, 1997, BURKE et al, 2000BELLMANN, 2001) or four waves (RHODES et al, 1995) have been observed. Cycles with three waves were on average 1.1 day longer and Corpora lutea regressed later than in animals with two waves.…”

“…ADAMS (1999) concluded from the available data that greater than 95 % of oestrous cycles are composed of either two or three follicular waves. Normally three to six follicles with a diameter of 4 to 5 mm occur after recruitment of follicles into in a follicular wave (SAVIO et al, 1988;SIROIS and FORTUNE, 1988;SUNDERLAND et al, 1994). However, the number of follicles, which are recruited in a wave seems to be higher (ADAMS, 1999;BELLMANN, 2001).…”