Amino acid availability of processed Brassica carinata meals in hybrid striped bass Morone chrysops x M. saxatilis

An earlier study showed that hybrid striped bass (Morone chrysops 9 x M. saxatilis d) diets containing 20 % animal meals and up to 30 % aerobically fermented (AF) carinata meal (Brassica carinata, CM) followed by a single wash with water (AFCM) or 30 % CM double-washed with water without AF (WCM), resulted in similar growth. However feed utilization and Fulton's condition factor of 30 % WCM were better. The current study investigated effects of AFCM and WCM on amino acid digestibilities using naive fish. Effects of AFCM and WCM on trypsin activity, and amino acid availability were determined using hybrid striped bass fed experimental diets for 127 and 148 days, respectively (after a growth trial). High (30 %) AFCM reduced all essential amino acids (EAA) and conditionally EAA (CEAA) except histidine, methionine and threonine. However, all EAA and CEAAs except lysine and cysteine were digested better in 30 %WCM than 30 % AFCM. High (30 %) CMs resulted in generally high serum free methionine and tryptophan, but less leucine for the first 9 h. However, 30 % WCM resulted in generally more serum free arginine and valine than 30 % AFCM. High CMs increased muscle free histidine. Generally, WCM resulted in more muscle lysine and valine than AFCM. Muscle methionine was increased by CMs. Both serum and muscle free total EAAs in hybrid striped bass fed 30 % WCM were elevated continuously over a longer period above the baseline levels. Using EAA:lysine, only muscle histidine were adequate for muscle synthesis over the 36-h period. Overall, amino acids were more available in WCM than AFCM.