Effect of prolonged infusion of small doses of LH-RH on the release of LH and ovulation in ewes during mid-anoestrus

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Abstract
Inspection of the ovaries and the occurrence of plasma LH [luteinizing hormone] elevations indicated that 8 out of 11 of the treated ewes had ovulated on the 4th, 5th or 6th day of LH-RH [LH-releasing hormone] infusion. Two ewes did not respond and 1 had only a small elevation of LH and no ovarian response. The ovaries of the ovulating animals were 2-3 times larger than before treatment and the corpora lutea seemed as large as those known to be functional. The uteri were also enlarged and appeared similar to the uteri of animals after ovulation at a normal estrus. The basal plasma LH concentrations during the first 3 days of infusion were lower than those during the next 3 days. The preovulatory preaks of LH in the 8 ovulating animals occurred on the 4th, 5th or 6th day of infusion; their values were much smaller than those observed at pro-estrus in cyclic ewes. These results indicate that ovulation can be induced in sleep without the use of a very high dose of neurohormone.