Observations in the present study are also consistent with earlier work in sheep in which induced premature ovulation of dominant ovarian follicles with injections of LH resulted in development of subfunctional CL. Subfunctional CL that developed as a consequence of the early induced ovulation in sheep likely resulted from the truncation of LH support during the final stages of development of the dominant ovarian follicles. In the present study, the exogenous LH mimicking the preovulatory LH surge was administered about 24 h before the time of the endogenous LH surge. Luteinization of the dominant ovarian follicle was, therefore, initiated about 24 h before the typical time of initiation of luteinization by the endogenous preovulatory surge of LH.
The dominant ovarian follicles in the present study thus did not have the final 24 h of episodic LH pulse stimulation before initiation of luteinization by the preovulatory LH surge. It is interesting, therefore, that secretion of progesterone by CL of animals in the control group, as well as size of CL, was similar to what is typical after initiation of luteinization by endogenous preovulatory surges of LH, which occur on the average at about 65 h after treatment of female cattle with PGF2a.