LH response of seasonally anovular Corriedale ewes acutely exposed to rams and estrous ewes

Abstract

Serial blood sampling before and after exposing four anovular Corriedale ewes to a group of rams and estrous ewes during the non-breeding season revealed a pattern of LH secretion similar to that previously observed in Merinos. Mean LH values doubled (P < 0.001) from 0.24 ± 0.06 μg L-1 (mean ± s.e.m.) before to 0.55 ± 0.05 μg L-1 after 2 h of visual, auditory, and odor exposure to rams and estrous ewes in an indoor facility. A non-significant (P < 0.17) increase of LH pulses per hour was also observed (0.7 ± 0.3 pulses per hour before compared with 1.3 ± 0.3 during stimulation). All four ewes had recently formed corpora lutea by five days after stimulation. Results are consistent with the pattern of sudden increase and sustained release of LH observed in other sheep breeds, particularly the Merino.