Stimulation of seasonally anovular merino ewes by rams. II. Premature regression of ram-induced corpora lutea

Ovulation was induced by rams in 74 of 91 seasonally anovular Merino ewes. The resulting corpora lutea (CL) were observed by laparoscopy and were found to either persist normally ($\text{38}\text{74}$), or regress prematurely ($\text{36}\text{74}$). In 32 of the latter ewes premature regression of the CL was followed by a second ovulation within 6 days of the introduction of rams.