Corpus luteum development and function in cattle with episodic release of luteinizing hormone pulses inhibited in the follicular and early luteal phases of the estrous cycle.

The influence of episodic LH pulses before and subsequent to ovulation on size and function of the corpus luteum (CL) in cattle was examined. Treatments were 1) control; 2) LHRH antagonist starting 2 days before the preovulatory LH surge (Antagonist [Ant] -2); 3) LHRH antagonist at initiation of the preovulatory LH surge (Ant 0); and 4) LHRH antagonist starting 2 days after the preovulatory LH surge (Ant 2). Treatments with an LHRH antagonist were continued until 7 days after the preovulatory surge. Diameter of the CL and concentrations of progesterone were monitored during the luteal phase that ensued after treatment. Maximum average diameters of CL were 9.5, 17.5, 21.6, and 28.8 mm for females from the Ant -2, Ant 0, Ant 2, and control groups, respectively (P < 0. 01). Compared with those in control animals, concentrations of progesterone in plasma were less (P < 0.01) in animals in which release of LH pulses was inhibited by treatment with antagonist. Arbitrary units under the curve for concentrations of progesterone during the luteal phase of the estrous cycle for Ant -2, Ant 0, Ant 2, and control groups were 19.6, 41.6, 43.6, and 142.2, respectively. There was no difference in circulating concentrations of progesterone (P > 0.1) among antagonist-treated groups. In conclusion, episodic release of LH pulses before, during, and after the time of the preovulatory surge of LH may stimulate development and function of the CL in cattle.