FACTORS THAT ENHANCE PITUITARY AND OVARIAN FUNCTIONS IN POSTPARTUM BEEF COWS (NALOXANE, GN-RH, PGF(2), INDOMETHACIN)

Currently and for several years ahead of it becomes ideal that each beef cow should produce one calf every year in order to sustain an economically viable cow-calf operation. In actual farm settings, however, this ideal condition is seldom achieved because of a variety of factors that act singly or in combination and influence pituitary and ovarian function postpartum. The studies in this dissertation address some of the factors and suggest some treatments that maybe employed in order to increase the percentage of cows that produce a calf every year under actual farm settings.;Ovulation rate to GnRH treatment was improved when PGF(,2) alpha was administered 30 hours previously. Cows that ovulated to GnRH treatment had greater GnRH-induced FSH releases than cows that failed to ovulate. Corpus luteum function which is generally abnormal after a GnRH-induced ovulation was eliminated when cows had greater GnRH-induced LH and RSH releases and was significantly improved by administering indomethacin shortly after GnRH treatment. Indomethacin administered at that time had no detrimental effects on embryo development.;Although naloxone, an opiod peptide antagonist, had no effect on the GnRH-induced release of pituitary LH, it depressed the peak amplitude of the GnRH-induced release of pituitary FSH in anestrous cows. Short term calf removal had no effect on the GnRH-induced LH release but enhanced the GnRH-induced FSH release. PGF(,2) alpha increase the release of LH but not FSH 4 to 6 hours later. PGF(,2) alpha also enhanced the amplitude of the GnRH-induced LH release, but not the FSH release.