Abstract

Reduced fertility often occurs when progestins are used to control the timing of oestrus in cattle and is espe-cially evident when a corpus luteum (CL) is not present in the ovary (Kinder et al., 1996). The lowered conception rates at the synchronised oestrus are associated with the development of abnormally large, “persistent” ovarian fol-licles as a result of increased secretion of LH. An under-standing of the endocrine regulation of persistent follicles is essential for development of methods to prevent ovula-tion of this aberrant structure in progestin-based oestrous control systems. The influence of time of luteal regression relative to follicle emergence on persistence of dominant follicles was evaluated in progestin-treated cows.

ML, Day, CR Burke, DP Nation, FM Rhodes, and KL Macmillan

Proceedings of the New Zealand Society of Animal Production, Volume 57, , 239-240, 1997