Effects of bovine growth hormone on plasma FFA concentrations and liver, muscle and carcass lipid content in rainbow trout, Salmo gairdneri Richardson

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Abstract
Bovine growth hormone (GH) given daily to rainbow trout, Sulmo gairdneri for 4 or 7 days at either 10.00 or 14.00 hours, significantly increased plasma free fatty acid (FFA) levels but had not effect on plasma cholesterol levels. Liver lipid content of the GH‐injected trout after seven injections was significantly lower than comparable controls in groups injected at both 10.00 and 14.00 hours. There were no apparent effects of GH on carcass or muscle lipid content although in fish injected and sampled at 14.00 hours there was a significant correlation between the number of injections and carcass lipid content.Changes in hepatosomatic index (HSI), liver, muscle and carcass lipid content, plasma FFA and cholesterol concentrations and somatotrop activity during food‐deprivation for up to 60 days are described. Despite significant decreases in liver and muscle lipid content and increases in plasma FFA levels in food‐deprived fish, there was no concomitant change in apparent somatotrop activity.The data are interpreted to indicate that although exogenous GH, in the doses used here, appears to stimulate mobilization of lipid reserves, particularly from the liver, there is no evidence that enforced changes in lipid reserves elicits a response of the endogenous somatotrop cells.