Growth hormone in mares and stallions: pulsatile secretion, response to growth hormone-releasing hormone, and effects of exercise, sexual stimulation, and pharmacological agents

Article Abstract:

The patterns of somatotropin secretion with other variables was studied in horses. In experiment 1, serial blood samples drawn revealed sex or season did not affect its secretion nor was there any diurnal variation. In the 2nd experiment, serial blood samples collected, with varying doses of exogenous hormone given, revealed its nondose-related, pulsatile nature. Experiment 3 noted exercise, exposure to an estrual mare, restraint, and epinephrine administration increased GH concentrtion. In experiments 4 and 5, varied doses of thyrotropin-releasing hormone and sulpride increased plasma prolactin concentration but did not affect GH concentration.

Exercise, Exercise physiology, Somatotropin, Sexual behavior in animals, Animal sexual behavior, Horse breeding

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Effects of pregnant mare's serum gonadotropin treatment on follicular populations and ovulation rates in prepubertal gilts with two morphologically different ovarian types

Article Abstract:

Pregnant mare's serum gonadotropin (PMSG) treatment resulted in comparable development of macroscopic follicles and ovulation rates in prepubertal sows with grape-type (GT) and honeycomb-type (HT) ovaries. PMSG treatment after ovariectomy also resulted in comparable number of large types (Classes 4 and 5) of follicles in GT and HT ovaries. The rates of atresia of Classes 4 and 5 were higher for HT than GT ovaries. PMSG injection decreased the atresion rates for the Class 5 follicles of HT ovaries. The higher ovulation rate in GT ovaries suggests ovarian morphology and ovarian compensation interaction .

Swine, Ovaries, Gonadotropin, Gonadotropins, Mares, Sows

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Effects of gonadotropin-releasing hormone infused in a pulsatile or continuous fashion on serum gonadotropin concentrations and ovulation in the mare

Article Abstract:

Two modes of gonadotropin infusion, continuous and pusatile, were compared to evaluate their effects on serum gonadotropin concentrations and ovulation in seasonally anestrous and in cycling mares. Experiment 1, which had 4 treatment groups recieving GnRH at different doses in either modes, showed that serum Luteinizing hormone (LH) increased earlier and more significantly in the pulsatile group and also ovulated the earliest. In the 2nd experiment, using cycling mares, LH concentrations were the lowest in the continuous infusion group.

Horses, Gonadotropin releasing hormone, Gonadorelin, Physiology

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