Treatments to Induce and Control Ovulations and Reduce the Incidence of Abnormal Luteal Phases in Postpartum Suckled Beef Cows

134 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.Anestrous postpartum suckled beef cows can be induced to ovulate by gonadotropin releasing hormone (GnRH) but the luteal phase following that ovulation is generally six to twelve days long. It was hypothesized that the presence of a luteolytic compound (prostaglandin F(,2)(alpha)) and the duration of the GnRH-induced LH surge are causes of the abnormal luteal phase. The aim of this dissertation was to determine the cause of abnormal luteal phases and to develop a procedure to induce and control fertile ovulations in both anestrous and cyclic postpartum suckled beef cows.Prostaglandin metabolite (PGFM) concentrations of suckled beef cows were elevated following parturition until four days postpartum and then declined linearly to a plateau on days 22 and 25 postpartum. A transient increase of PGFM occurred following the administration of oxytocin. Intrauterine infusions of indomethacin suppressed the basal concentrations and the oxytocin-inducible release of PGFM and enhanced corpora lutea life-span and function following a GnRH-induced ovulation.Short-term calf removal enhanced the GnRH-induced LH release when GnRH was administered by a method that has been demonstrated to prolong the GnRH-induced LH release (subcutaneous administration in gelatin capsules). The duration of the GnRH-induced LH release on subsequent ovarian function, however, was difficult to discern.Progestin treatment prior to GnRH administration was incorporated into a prostaglandin F(,2)(alpha) estrous synchronization program to induce and control fertile ovulations in both anestrous and cyclic postpartum suckled beef cows. Progestin treatment prior to GnRH reduced the incidence of abnormal luteal phases in the anestrous cows. The GnRH-induced LH release was enhanced by the progestin treatment and PGFM concentrations appeared to be lower and less variable. There were no detrimental effects on ovarian function or first service pregnancy rates in the cyclic cows due to the progestin-GnRH treatments. The progestin treatment enhanced the first service pregnancy rates for the anestrous cows.It was concluded that progestin-GnRH treatment enhanced the GnRH-induced LH release and suppressed PGFM concentrations and induced and controlled fertile ovulations in both anestrous and cyclic postpartum suckled beef cows.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD