Evaluation of crystalline amino acid test diets including pH adjustment with red drum (Sciaenops ocellatus) and hybrid striped bass (Morone chrysops × Morone saxatilis)

The red drum and hybrid striped bass are cultured in the United States for both stock enhancement and food production. Based on previous observations in this laboratory, the hybrid striped bass appeared to use pH-adjusted crystalline amino acid test diets more readily than the red drum. Therefore, the present study was conducted to directly compare responses of red drum and hybrid striped bass fed crystalline amino acids with and without neutralization (pH 7) relative to an intact protein diet composed of red drum muscle. Fifteen red drum (initially 1.5-2.5 g each) and 15 hybrid striped bass (4.5-5.5 g each) were placed separately in each of nine 38-l aquaria (18 aquaria total) as part of a brackish water (7‰) recirculation system. Each diet was randomly assigned to three replicate tanks of red drum and hybrid striped bass. After a 55-day feeding period, both red drum and hybrid striped bass fed the intact protein diet had significantly (P < 0.05) greater weight gain, feed efficiency and protein efficiency ratio values compared to those fed the crystalline amino acid diets. However, hybrid striped bass used the crystalline diets more efficiently than red drum relative to the intact protein diets. In addition, no differences were detected in red drum or hybrid striped bass performance when fed the crystalline amino acid diets regardless of pH adjustment.