The objectives of this study were to evaluate the growth promotion effect of growth hormone releasing hormone (GHRH) plasmid injected in piglets and measure protein turnover in piglets injected with different amount of GHRH plasmid. It was found that the injection and expression of pGHRH gene plasmid in skeletal muscle of pigs stimulates GHRH and GH
excretion and increases circulating IGF-I concentration in piglets, improves growth performance and feed conversion.
Protein deposition increased after injecting pGHRH gene plasmid in muscle of piglets. This increase was caused by an increase in protein synthesis which exceeded the concomitant increase in protein breakdown. A dosage of 1 mg gave maximum effects of the pGHRH gene plasmid on protein metabolism in piglets. At higher doses, the feedback regulation of SS may limit the responses of protein metabolism to pGHRH gene plasmid.