Quantitative Dietary Threonine Requirement of Juvenile Striped Bass Morone saxatilis

A 10-wk feeding trial was conducted to quantify the dietary threonine requirement of juvenile striped bass Morone saxatilis . The basal diet was analyzed to contain 42% crude protein with a calculated digestible energy (DE) level of 3,200 kcal/kg. L-threonine was added to the basal diet to yield five dietary treatments of 0.61, 0.81, 1.00, 1.18, and 1.40% available threonine on a dry-matter basis. Weight gain, specific growth rate (SGR), feed conversion ratio (FCR) and apparent nitrogen utilization (ANU) were significantly ( P < 0.05) affected by dietary threonine concentrations. Least-squares regression analysis of weight gain, SGR, FCR, and ANU indicated dietary threonine requirements (±SE) of 1.00 ± 0.19, 0.91 ± 0.11, 1.06 ± 0.09 and 1.13 ± 0.22% of dry diet, respectively. From these results, the average recommended dietary threonine requirement of juvenile striped bass is 1.03% of dry diet, 2.45% of dietary protein or 3.22 mg/kcal DE.