the effect of different levels of niacin in diet on immunological and blood biochemical parameters of juvenile carp (cyprinus carpio)

This experiment was conducted to examine the effect of different levels of niacin on some immunological and blood biochemical parameters of juvenile carp. a control diet (containing 30 mg niacin kg^-1 commercial diet) and four other diets were prepared to contain 50, 70, 90 and 110 mg niacin per kg of commercial diet. fish with initial average weight of 25 ± 0.28 g were allotted to 15 circular tanks of 300 l capacity at a density of 12 fish per tank and fed the experimental diets to satiation triple daily for 56 days. at the end of feeding trial, lysozyme activity, lymphocyte, monocyte, neutrophil and basophil percentage were not significantly different from the control. the blood protein, albumin and glucose values of fish fed 90 and 110 mg niacin kg^-1 diet were significantly higher than control group. the triglyceride and total cholesterol values of fish fed different levels of niacin were not significantly different compared to control group. fish fed 70 up to 110 mg niacin kg -1 diet showed significantly higher high density lipoprotein (hdl) than 50 mg niacin^-1 kg diet and control. the results confirmed that 90 mg niacin kg^-1 affected performance of juvenile common carp through effect on total protein and glucose values.