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Title: EFFECTS OF PORCINE SOMATOTROPIN ON CIRCULATING TESTOSTERONE CONCENTRATIONS IN BOARS AND MECHANISM OF ACTION

Author
item Wise, Thomas
item Klindt, John
item Ford, Johny
item BUONOMO, FRANCES - MONSANTO AGRICULTURAL CO

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The pituitary gland makes chemicals called hormones which affect reproduction, growth and health of animals. An understanding of how the pituitary is regulated and how it functions will ultimately lead to improved domestic animal production. Studies were conducted to determine effects of exogenous growth hormone on pituitary and gonadal function in boars. Both testosterone and luteinizing hormone were reduced following growth hormone treatment in different age groups of boars. Reductions in circulating androgens in conjunction with increases in growth and efficiency from growth hormone treatment in boars may provide a useful management tool to increase efficiency of lean meat production and decrease boar androgen and labor.

Technical Abstract: Four experiments were conducted to elucidate the effects of porcine somatotropin (pST, growth hormone) on circulating testosterone concentrations in boars. In Exp. 1, jugular cannulated obese boars were administered 4 mg recombinant (r) pST/d for 24 d before collection of samples at 15-min intervals over 6 h for measurement of pST, testosterone, and LH. Somatotropin treatment decreased plasma concentrations of testosterone and LH (P<.05). In Exp. 2, White composite boars were administered rpST with implants (4 mg/d) for 10 to 28, 16 to 28, or 22 to 28 wk of age. Reductions in testosterone concentrations were proportional to the length of time rpST was administered; boars treated for 18 wk had the lowest testosterone concentrations. Concentrations of LH declined throughout the study in rpST-implanted boars but remained static in untreated, control boars. In Exp. 3, i.v. injection of pituitary pST (USDA-B1; 5 ug/kg BW) into cannulated (jugular) White composite and Meisha boars resulted in an acute increase in circulating LH followed by an increase in testosterone concentrations. Multiple injections, two or four per d, of 5 ug pST/kg BW resulted in decreased testosterone concentrations in White composite boars. Depression of circulating concentrations of androgens in boars requires extended periods of pST treatment.