An experiment was conducted to investigate the effect of dietary
chromium picolinate supplement on growth and haematology parameters of grass carp, Ctenopharyngodon idellus. Six diets with increasing dietary
chromium picolinate levels 0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg kg(-1) were fed to triplicate groups of 20 fish (initial weight of 12.78 +/- 1.16 g, mean +/- SD) in a flow water system for 10 weeks. Fish fed the diet supplemented with 0.8 mg Cr kg(-1) had significantly improved
weight gain (WG), feed efficiency ratio (
FER), protein efficiency ratio (PER) and
protein retention (PR). Fish fed high-
chromium diets exhibited lower whole-body crude
lipid contents than fish fed low-
chromium diets.
Liver glycogen concentrations for fish fed the diet with 0.2 mg Cr kg(-1) was the highest (77.67 mg g(-1)). Fish fed the diet supplemented with 1.6 and 3.2 mg Cr kg(-1) had significantly lower
liver glycogen concentrations than other groups (P < 0.05). The highest serum
insulin concentrations were observed in fish fed the diet supplemented with 0.8 mg Cr kg(-1), but serum
insulin concentrations decreased (P < 0.05) when dietary supplementation of
chromium was higher than 0.8 mg Cr kg(-1).
Cholesterol concentrations decreased in direct proportion to dietary
chromium level and achieved the lowest level when the fish were fed the 0.8 mg Cr kg(-1) diet, but increased when the fish were fed the diet with more than 0.8 mg Cr kg(-1) (P < 0.05). Fish fed the diet supplemented with 0.8 mg Cr kg(-1) had higher
triglyceride and
high-density lipoprotein cholesterol (HDL-C) concentrations compared to other treatments. The results of the present study suggested that
chromium picolinate could modify serum
carbohydrate and lipid metabolism profile, and that the optimal dietary
chromium level was 0.8 mg kg(-1) for grass carp according to growth.