DIETARY VALINE REQUIREMENT FOR JUVENILE GIBEL CARP (CARASSIUS AURATUS GIBELIO)

A 65d growth trial was conducted to investigate the effect of different dietary valine levels on the growth performance and feed utilization of juvenile gibel carp (Carassius auratus gibelio) average body weight: (3.17?.01)g, and to determine the dietary valine requirement for gibel carp. Eight isonitrogenous (crude protein content: 38%) and isoenergetic (gross energy: 17.00 kJ/g) semipurified diets were formulated with the graded supplemental levels of crystalline valine (0.54, 0.79, 1.04, 1.29, 1.54, 1.79, 2.04 and 2.29% dry diet, respectively), using casein, gelatin and crystalline amino acids as the main dietary protein sources. The eight experimental diets were determined to contain valine of 0.66, 0.85, 1.07, 1.22, 1.46, 1.70, 1.86 and 2.12% dry diet, respectively. Contents of other essential amino acids in the diets were formulated to simulate the amino acid profile of gibel carp muscle protein. Each diet was fed in triplicate groups and 30 fish each group were stocked in a flow-through system (water flow speed 0.5 L/min) consisting of 24 polyvinyl quadrate tanks (70 cm?5 cm?0 cm; water volume 150 L). Fish were fed to satiation by hand twice a day at 8:00h and 16:00h. Dietary valine levels significantly influenced specific growth rate, feed efficiency and protein retention efficiency (P0.05), but significantly affect the serum glutamine concentration significantly (P0.05), except the body ash contents (P<0.05). Polynomial regression analysis between the specific growth rate and the dietary valine levels indicated that the dietary valine requirement of gibel carp was 1.72% of dietary valine (on a dry matter basis) and 4.53% in terms of dietary protein.