Effects of growth hormone-releasing factor and feed intake on energy metabolism in growing beef steers: net hormone metabolism by portal-drained viscera and liver

The effects of growth hormone-releasing factor (GRF) and feed intake on the serum concentration and visceral metabolism of growth hormone (GH), insulin-like growth factor-I (IGF-I), somatostatin, glucagon and insulin were determined in six crossbred steers. Results showed that GRF elevated serum concentrations of insulin, IGF-I and GH independent of splanchnic metabolism. On the other hand, the elevation of arterial concentrations of insulin and glucagon resulting from the increase in feed intake was mediated by the hormones' release from portal-drained viscera.