Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 1995
Publication Date: N/A
To characterize ovarian follicular dynamics and selection of multiple ovulatory follicles in cattle producing dizygotic twins, ovarian follicular development was monitored for one estrous cycle in six mature cows selected for the natural expression of multiple ovulations. Ovaries were examined by ultrasonography on alternate days from d 3 of the estrous cycle (estrus = d 0) to d 5 of the subsequent cycle using a 7.5 MHz linear array transrectal probe. Three cows had an estrous cycle with three follicular waves and three cows with two waves. Duration of the 3-wave and 2-wave estrous cycles were 22.3 d and 19.7 +/- .8 d, respectively. Means (+/- SEM) for interval from estrus to maximum follicle diameter and for maximum diameter of the largest and second largest follicles for wave 1, 2 and 3 were: 10.5 +/- .9 d and 15.0 and 12.5 +/- .8 mm, 18.0 +/- .9 d and 14.0 and 12.0 +/- .8 mm, and 22.0 +/- .9 d and 13.7 and 13.0 +/- .8 mm, respectively, for three-wave cycles, and 8.5 +/- .9 d and 12.8 and 11.7 +/ .8 mm and 20.0 +/- .9 d and 15.3 and 13.3 +/- .8 mm, respectively, for two-wave cycles. Twin ovulations occurred in five of six cows during the monitored estrous cycles (one single ovulation) compared to five twin and one triplet ovulation in the previous cycle. Distribution of corpora lutea (CL) between the left (Lt) and right (Rt) ovary in two estrous cycles was: 1 CL Lt = 1 cow, 2 Lt = 1, 3 Lt = 1, 2 Rt = 3, and Lt&Rt = 6. Emergence of multiple large follicles within a majority of the follicular waves suggests that selection for twin ovulations in this population altered follicular dynamics in that multiple rather than single dominant follicles are selected within a follicular wave. Dominant follicles were not retained between waves.