COMPARISON OF GROWTH HORMONE-RELEASING FACTOR AND SOMATOTROPIN - LIPID AND GLUCOSE-METABOLISM IN DAIRY-COWS

Lactating, primiparous Holstein cows were continuously infused for 63 d with either recombinant growth hormone-releasing factor or recombina nt bST or were not infused (control). The releasing factor and bST tre atments reduced fat synthesis from acetate and lipoprotein lipase acti vity in omental adipose tissue. Also, both treatments increased hormon e-sensitive lipase activity per gram of adipose tissue and reduced fat ty acid esterification per milligram of protein in adipose tissue. Pro tein concentration in adipose tissue with both treatments was greater than that of the control, although the protein concentration was less in adipose tissue from cows treated with the releasing factor than fro m those treated with bST. In mammary tissue, releasing factor increase d fat synthesis from acetate more than did bST treatment, but percenta ges of fat or short-chain fatty acids in milk were not different betwe en treatments, nor were differences significant between treatments and control for fatty acid esterification or lipoprotein lipase activity in mammary tissue or gluconeogenesis and fatty acid esterification in liver. We conclude that protein concentration was lower in omental adi pose tissue of cows treated with releasing factor than that in tissue of cows treated with bST, although both treatments similarly suppresse d synthesis of fat from acetate and activity of lipoprotein lipase.