The inter-ovarian distribution of dominant follicles is influenced by the location of the corpus luteum of pregnancy

摘要

Primiparous cows from a herd in the Waikato region of New Zealand were examined over a 2-year period (33 in year 1 and 28 in year 2). Ovarian follicles were observed daily by trans-rectal ultrasonography commencing within 9 days of calving. Dominantfollicles were described as occurring on the ovary on the same side as the corpus luteum of the preceding pregnancy (ipsilateral ovary) or on the opposite side to the corpus luteum of the preceding pregnancy (contralateral ovary), and as occurring on the left or right ovary. Results from the cattle examined during year 1 (15 Friesian and 18 Jersey) were analysed for the effects of breed. There was a bias towards the contralateral ovary for the 1st dominant follicle post partum in both breeds (70%; P<0.05). A breed interaction was observed with the 2nd dominant follicle post partum with a bias towards the contralateral ovary in the Friesian (93%; P<0.05); but not the Jersey cattle (50%). In year 2, all cows were Friesian, and there was again a biased distribution of the 1st dominant follicle towards the contralateral ovary (89%; P<0.05) and for the combined distribution of the first 3 dominant follicles post partum (76%; P<0.05) and the 1st ovulatory follicle (71%; P<0.05). Pooled data for the location of the 1st dominant follicle from both years was analysed; only 1 first dominant follicle was observed on a left ovary in the 29 cases where the preceding pregnancy was also on the left side.