Dietary valine requirement for juvenile grass carp (Ctenopharyngodon idella)

Abstract:

A 75d feeding trail was conducted to determine the dietary valine requirement for juvenile grass carp (Ctenopharyngodon idella). Seven isonitrogenous diets with graded levels of valine ranging from 6.3 to 15.8 g/kg of dry diet were fed to triplicate groups of fish with an average initial body weight of 1.35 g, respectively. The results showed that the weight gain rate, feed efficiency and protein retention efficiency were significantly affected(P<0.05). Weight gain rate and protein retention increased significantly with increasing dietary valine levels from 6.3 to 12.6 g/kg, but decreased significantly with further increase to 15.8 g/kg. Feed efficiency increased significantly with increasing dietary valine levels from 6.3 to 12.6 g/kg, but kept stable with increase to 15.8 g/kg. Fish essential amino acids, leucine, isoleucine, total amino acids and whole fish content were not affected significantly by dietary valine levels (P>0.05). ALT (glutamic-pyruvic transaminase) activity in hepatopancreas reached the maximum value at the dietary valine level of 11.0 g/kg, but there was no significant difference between the groups. AST (glutamic-oxalacetic transaminase) activity in hepatopancreas was not affected significantly by dietary valine levels (P>0.05). Second-degree polynomial regression analysis based on weight gain rate, protein retention efficiency and feed efficiency indicated that the requirements of dietary valine for fingerling grass carp were 12.79-13.68 g/kg of dry diet, 3.76%-4.02% of dietary protein, respectively.