Physiological, biochemical and histometric responses of Nile tilapia (Oreochromis niloticus L.) by dietary organic chromium (chromium picolinate) supplementation

Chromium has been recognized as a new and important micro-nutrient, essential for both human and animal nutrition. this study was conducted to evaluate the appropriateness and/or the use of safety level of dietary chromium picolinate (cr-pic), and its effects on the physiological responses, the histometric characteristics, and the chemical analysis of dorsal muscles of mono-sex nile tilapia, oreochromis niloticus. niloticus. a total of 420 fingerlings (28.00±0.96 g) were randomly distributed into 21 fiberglass tanks representing seven treatments at a rate of 20 fish m^-3. the control fish group (t1) was fed a cr-pic free basal diet. other fish groups were fed the basal diet supplemented with 200 (t2), 400 (t3), 600 (t4), 800 (t5), 1000 (t6) and 1200 μg cr-pic kg^-1 diet (t7). diets were offered to fish at a feeding rate of 3% of life body weight for 12 weeks. results revealed that blood hematological parameters (hemoglobin, red blood cells, packed cell volume, mean corpuscular hemoglobin concentration, blood platelets, and white blood cells lymphocytes); serum biochemical measurements (total testosterone, high density lipoprotein, total protein, albumin, and globulin); and the dry matter and crude protein of the fish dorsal muscles all have significantly increased (p 6 0.05) in the t3 treatment compared with the other treatments. meanwhile, no significant differences were found among all treatments with regard to the histometric characteristics. it can be concluded that cr-pic at 400 μg kg^-1 diet (t3) seems to be the most appropriate level for o. niloticus fingerlings.