Dietary Histidine Requirement for Juvenile Large Yellow Croaker, Pseudosciaena crocea R.

Dietary histidine requirements for large yellow croaker (initial average weight, 6.0 +/- 0.10 g) were quantified by feeding isonitrogenous (crude protein 44%) and isocaloric (20 KJ/g) amino acid test diets with graded levels of histidine [0.45% (D1), 0.66% (D2), 0.78% (D3), 0.98% (D4), 1.24% (D5) and 1.40% (D6) of dry diet]. Each diet was randomly assigned to triplicate floating sea cages (1.0 x 1.0 x 1.5 m), 60 fish/cage. At the end of the 51 day experiment, the final weight (FW) and weight gain (WG) of large yellow croaker showed a positive correlation to increasing dietary histidine content (up to 0.78%), and thereafter declined. The growth of fish fed the D6 diet was significantly lower than fish maintained on the D2 and D3 diets; however, there were no significant differences in the growth of large yellow croaker among all the dietary treatments except D6. Fish fed the D3 diet had the highest FW and WG. The shift in feed efficiency (FE) values of fish fed D1 to D5 diets increased as dietary histidine content increased, and significantly decreased in fish fed the D6 diet. Based on the second-degree polynomial regression analyses of the growth data, optimum histidine requirement for juvenile large yellow croaker was 8.7 g/kg dry diet, (18.8 g/kg-20.8 g/kg of dietary protein within 95% confidence interval).