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Title: ENDOCRINE AND METABOLITE RESPONSES TO PORCINE GROWTH HORMONE ADMINISTERED BY SUSTAINED RELEASE IMPLANT FOR DIFFERENT LENGTHS OF TIME IN MALE PIGS

Author
item Klindt, John
item BUONOMO, FRANCES - PROTIVA-MONSANTO COMPANY
item Wise, Thomas
item Yen, Jong Tseng

Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Excessive fat production reduces efficiency of pork production and is a concern of the pork industry. Not castrating boars and administration of porcine somatotropin (pST) are among methods proposed to reduce unwanted fat. Products from intact boars are contaminated by boar taint, an androgenic pheromone which produces an objectionable odor upon cooking. Previous work showed that treatment of boars for 6 wk with pST reduced boar odor in loin chops. The present study investigated the effect of treatment of boars for different periods before slaughter, 6, 12 and 18 wk, on hormonal and metabolite responses. Somatotropin was administered with sustained release implants. The results show that castration and prior treatment of boars significantly influences hormonal and endocrine responses. Greatest responses in the serum measures quantitated, with the exception of IGF-I were with administration of pST during the peripubertal and postpubertal periods, 16 to 28 wks of age. The IGF-I response was greatest during the prepubertal period, 10 to 18 wks of age. The greatest responses in growth and carcass characteristics were seen in boars in which treatment was initiated during the peripubertal period, at 16 wks of age. These data presented herein combined with the growth and carcass data presented previously indicate there are few advantages of initiating pST treatment before about 16 wks of age, about 110 to 120 pounds live wt. Initiation of pST treatment of boars at this age results in significant improvements in growth, carcass quality, including boar taint, and favorable changes in circulating concentrations of growth regulating hormones.

Technical Abstract: Effect of long-term administration of growth hormone (GH) on serum concentrations of hormones and metabolites was investigated in boars and barrows. At 10 wk of age pigs were assigned to 6 treatments (n=10/group): non-implanted boars and barrows; boars, implanted from 22 to 28 wk of age; boars implanted from 16 to 28 wk of age; and boars and barrows implanted from 10 to 28 wk of age. Recombinant porcine GH was administered with sustained release implants designed to deliver a dose of 4 mg/d. Pattern of administered GH in the serum suggests the presence of testes and prior treatment with GH influence GH clearance. Somatotropin treatment elevated serum concentrations of GH and increased serum levels of glucose, insulin, IGF-I and IGF-II in both intact and castrate animals. However, during the prepubertal period of 10 to 16 wk GH-treated intact males were resistant to the diabetogenic actions of GH, while, significantly increased serum levels of glucose and insulin occurred in GH-treated castrates during this period. Changes in serum levels of IGF-I throughout the study and insulin after the first 6 wk followed the pattern of circulating GH concentrations in the treated animals. Serum concentrations of IGF-II were increased following GH administration, but, in contrast to the IGF-I response IGF-II levels remained elevated as GH concentrations waned in the latter portion of an implant period. Maintenance of higher serum levels of IGF-II may be less dependent upon GH than are insulin and IGF-I. Administration of GH to intact males is more efficacious in altering metabolites and hormones, with the exception of IGF-I, during the peripubertal and postpubertal periods than during the prepubertal period.