It is therefore assumed that LHRH antagonist-induced modulations of FSH concentrations cannot explain why luteal function is suppressed in cattle treated with the LHRH antagonist during the period of luteal development.
In summary, inhibition of release of episodic LH pulses from 2 days before the preovulatory surge of LH until Day 7 of the estrous cycle had the greatest inhibitory effect on development of a CL. Similarly, diameter of the CL was decreased as a result of inhibition of LH release starting at the time of and 2 days after the preovulatory surge of LH up to Day 7 of the estrous cycle. Concomitantly, function of the resulting CL was suppressed by inhibition of LH release at different times relative to the preovulatory surge of LH, as evidenced by reduced capacity to secrete progesterone.
In conclusion, final maturation of the preovulatory follicle may be dependent on episodic release of LH pulses during the last 48 h before the preovulatory surge of LH, and it is required for development of a CL of typical diameter and function in cattle. Episodic release of LH pulses subsequent to the preovulatory surge of LH is also required for development of the CL in cattle. The relatively large amounts of LH released during the preovulatory surge of LH are not sufficiently luteotropic to support secretion of progesterone similar to that of a normal CL. Theca, granulosa, and luteal cells require episodic stimulation by LH pulses during the periovulatory stages of the estrous cycle for development of a luteal structure with typical diameter and steroidogenic capacity in cattle.