Effect of dietary energy intake and exogenous porcine growth hormone administration on circulating porcine growth hormone concentration and response to human growth hormone-releasing factor administration in growing swine. 
In a 2 x 2 treatment array (n = 4 pigs/treatment), the effects of feed intake (ad libitum vs. restricted to 60% ad libitum) and the daily administration of excipient buffer or porcine pituitary-derived growth hormone (GH) at a dose of 100 micrograms/kg body weight per day on serum GH profile and human growth hormone-releasing factor (hGRF) response were examined in barrows weighing 55 kg.  Feed intake treatment was implemented from 25 to 55 kg live weight.  Buffer or GH treatment was implemented for 10 d before sampling.  After GH treatment, the integrated serum GH concentration area was 25% greater in barrows fed restrictively.  Data are consistent with the suggestion that GH dose to improve the efficiency of lean tissue deposition be adjusted according to feeding regimen.  The serum GH response to hGRF was also altered by level of feed intake.  The ad libitum feeding of buffer-treated animals resulted in a monophasic serum GH response to hGRF, whereas barrows fed restrictively had a biphasic response to hGRF.  Together, these data suggest that feed intake pattern alters GH secretion and as such could influence the practical implementation of somatotropin as a metabolism modifier in swine.