Submitted to: Animal Science Progress Report
Publication Type: Other
Publication Acceptance Date: 7/23/1997
Publication Date: N/A
Technical Abstract: Age-dependent interactions between environmental temperature and pGH treatment on the function of the somatotrophic axis were evaluated in the neonatal pig. At 3 d of age, 40 piglets received intraperitoneal implants of either recombinant pGH (0.5 mg/day; n=20) or vehicle (Control; n=20). Piglets were maintained with sows at either a low (20C; n=20) or high (32C; ;n=20) temperature. At 4 wk and 6 wk of age, 10 of the piglets from each group were sacrificed for tissue and blood collection. Blood samples were analyzed for serum GH, IGF-1, and IGF-2. Liver RNA was analyzed for mRNAs specific for the GH receptor, IGF-1, IGF-2, and IGF binding protein 3 (IGFBP-3). There was no effect of pGH treatment (P>0.10) on ADG, however, there was an effect of both age (P<0.002) and temperature (P<0.003) on ADG. Serum GH was elevated (P<0.004) by pGH treatment, and was greater (P<0.02) in the 4 wk age group. Serum IGF-1 was enhanced (P<0.007) by pGH treatment tand in the 6 wk age group (P<0.01). Serum IGF-2 tended (P<0.08) to be elevated by pGH treatment. Liver GH receptor mRNA was unaffected by pGH treatment, but was greater in the 6 wk age group (P<0.0001) and in piglets maintained at the high temperature (P<0.04). IGF-1 mRNA was enhanced by pGH treatment (P<0.0003) and by exposure to the high temperature (P<0.03), but did not differ between age groups. IGF-2 mRNA was greater (P<0.002) in the 4 wk age group and in piglets maintained at the high temperature, but was unaffected by pGH treatment. IGFBP-3 mRNA was elevated by pGH treatment (P<0.04) and in the 6 wk weaning groups (P<0.0008). These results demonstrate developmental alterations in the somatotrophic response of neonatal pigs to pGH treatment and emphasize the importance of environmental conditions which can alter these responses.