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 s ize and function of the corpus luteum (CL) in cattle was examined. Treatmen ts were 1) control; 2) LHRH antagonist starting 2 days before the preovulat ory LH surge (Antagonist [Ant] -2); 3) LHRH antagonist at initiation of the preovulatory LH surge (Ant 0); and 4) LHRH antagonist starting 2 days afte r the preovulatory LH surge (Ant 2). Treatments with an LHRH antagonist wer e continued until 7 days after the preovulatory surge. Diameter of the CL a nd concentrations of progesterone were monitored during the luteal phase th at 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 gr oups, respectively (P < 0.01). Compared with those in control animals, conc entrations of progesterone in plasma were less (P < 0.01) in animals in whi ch release of LH pulses was inhibited by treatment with antagonist. Arbitra ry units under the curve for concentrations of progesterone during the lute al 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-treat ed groups. In conclusion, episodic release of LH pulses before, during, and after the time of the preovulatory surge of LH may stimulate development a nd function of the CL in cattle.