Effects of LH-RH analogue on LH release and ovarian function in ovarian quiescent heifers.

Abstract

A total of 10 cases of ovarian quiescent heifers were assigned to 4 treatment groups. Heifers of Group I(n=3), II(n=3), III(n=3) and IV(n=1) were treated with a single intramuscular (IM) injection of 100μg, double IM injections of 100μg at 1 hr interval, single IM injection of 200μg and 400μg of LH-RH analogue, respectively. Changes of LH, estradiol-17β (E2), progesterone (P) levels in peripheral blood and ovarian alteration were examined before and after the treatment. The LH level increased quickly in all cases, reaching a peak of 72.3±42.9 (SD) ng/ml about 2 hr after and returned to a basal level about 7 hr after treatment. There was no significant difference in post-treatment maximum LH levels among Groups I, II and III. Ovulation was induced in 8 cases 35.5±5.3 hr after LH peak. Patterns of ovarian response after treatment were classified into 6 types according to changes of ovarian structure and P and E2 levels. No distinct disparity was found among the 6 types in pre-treatment LH and E2 levels, post-treatment maximum LH levels and amount of released LH, respectively. No correlation between the post-treatment LH release and the succeeding ovarial response was observed.