EFFECT OF REDUCTION OF SUPPLEMENTARY DIETARY VITAMINS ON THE STRESS-RESPONSE OF CHANNEL CATFISH ICTALURUS-PUNCTATUS

The influence of reduced amounts of supplemental vitamins on the stres s response of channel catfish Ictalurus punctatus was determined. Fish were fed diets with reduced levels of supplemental vitamin C, niacin, riboflavin, pantothenic acid, pyridoxine or thiamine, or with reduced amounts of the total vitamin supplement typically added to catfish fe ed. Fish were confined for 6 h and blood samples taken at 0, 1 and 6 h of confinement and 12 h after release. Plasma chloride and osmotic pr essure were consistently stable throughout the experiment and were not influenced by the diet or the stress imposed. Cortisol concentrations were elevated at 1 and 6 h of confinement but recovered to preconfine ment concentrations 12 h after release. The cortisol response varied i n some of the groups; however, no consistent effects due to the vitami n concentrations were observed. The lack of supplemental vitamins in t he food did not impair the ability of the fish to mount or maintain co rtisol secretion. The feed ingredients may contain enough vitamins to support cortisol synthesis or the fish may be acquiring sufficient add itional vitamins from the pond environment or from intestinal bacteria .