Effects of various mating stimuli on pituitary release of luteinizing hormone in the gilt

Abstract

Twenty-four nulliparous crossbred gilts approximately 9 months of age were assigned to either a naturally mated (NM), artificially inseminated (Al) or non-mated control group (C). All gilts were fitted with indwelling cephalic cannulas for collection of blood samples for subsequent hormonal analyses every 10 min for the first 24 hr of the periestrous period. Plasma luteinizing hormone (LH) concentrations were not affected by type of mating. The mean duration of the LH surge for Al group was less than the C or NM groups (44.5 vs 67 and 87 hr (P<.05)). Mean maximal LH concentrations for the Al and NM groups occurred prior to the control group (P> 05). Area under the LH release curve and number of episodic surges were not different for the three treatments. Length of standing estrus and exposure time to back pressure were not different among treatment groups. The results suggest that stimulation of the pelvic region during either natural mating or artificial insemination did not enhance release of LH. Mated gilts did exhibit different secretory patterns of LH release than non-mated gilts.