DIETARY METHIONINE REQUIREMENT OF FLORIDA POMPANO
Methionine is one of the ten dietary essential amino acids required for normal health and growth of fish. The dietary methionine requirement of Florida pompano (Trachinotus carolinus), a high-valued food fish in the U.S., needs to be determined for developing practical diets for its commercial aquaculture.
A feeding trial was conducted to determine the dietary methionine requirement of Florida pompano. Six diets were formulated with zein, fish meal, soy protein concentrate, and crystalline amino acids to contain 46% crude protein (CP), 9 kcal/g digestible energy- to-CP ratio, and amino acid profile matching that of pompano whole-body except methionine. The diets contained graded levels of methionine (0.44-2.04% of diet) and a constant level of cystine (0.22% of diet). Pompano (mean body weight 23 g) were fed each experimental diet in four replicate groups for eight weeks. At the end of the experiment, there was no significant difference (P > 0.05) in survival rate (87.5-93.8%) of pompano across the treatments. Pompano fed the lowest level of methionine had significantly lower specific growth rate (0.77%/d), daily growth index (0.79 g1/3/d), protein efficiency ratio (0.78) and protein retention (13.2%), and higher feed conversion ratio (3.16) than pompano fed the other diets. Weight gain data indicate the optimum dietary methionine requirement of pompano to be 1.17% (2.54% of CP) based on broken-line regression (R2 = 0.72) and 1.60% (3.48% of CP) based on second-order polynomial regression (R2 = 0.71; Figure 1).
A feeding trial was conducted to determine the dietary methionine requirement of Florida pompano. Six diets were formulated with zein, fish meal, soy protein concentrate, and crystalline amino acids to contain 46% crude protein (CP), 9 kcal/g digestible energy- to-CP ratio, and amino acid profile matching that of pompano whole-body except methionine. The diets contained graded levels of methionine (0.44-2.04% of diet) and a constant level of cystine (0.22% of diet). Pompano (mean body weight 23 g) were fed each experimental diet in four replicate groups for eight weeks. At the end of the experiment, there was no significant difference (P > 0.05) in survival rate (87.5-93.8%) of pompano across the treatments. Pompano fed the lowest level of methionine had significantly lower specific growth rate (0.77%/d), daily growth index (0.79 g1/3/d), protein efficiency ratio (0.78) and protein retention (13.2%), and higher feed conversion ratio (3.16) than pompano fed the other diets. Weight gain data indicate the optimum dietary methionine requirement of pompano to be 1.17% (2.54% of CP) based on broken-line regression (R2 = 0.72) and 1.60% (3.48% of CP) based on second-order polynomial regression (R2 = 0.71; Figure 1).