Evaluation of Digestible Energy and Protein for Growth and Nitrogen Retention in Juvenile Florida Pompano, Trachinotus carolinus

Juvenile Florida pompano (6.3 6 0.50 g) were fed 1 of 12 diets formulated with an array of crude protein (340, 380, 420, 480, or 500 g/kg diet) and crude lipid (60, 100, 120, 160, or 180 g/kg diet) levels and estimated digestible protein to digestible energy (DP/DE) of 18.9–26.8 mg/kJ. In a second trial, apparent protein and energy digestibilities were empirically determined and coefficients used to calculate actual digestibilities. Digestible energy (DE) intake was 4.2–13.0 kJ/fish/d, and digestible protein (DP) intake was 0.13–0.32 g/fish/d. Average daily gain increased as a function of both DP and energy. Growth increased with increasing DP in all diets containing 24.0 mg/kJ DP/DE or greater until a plateau at 366 g DP/kg. Nitrogen gain was also a function of both DP and DE. Increasing energy at constant protein improved protein utilization. DP to maximize growth and nitrogen gain was between 356 and 366 g/kg. DE to attain maximum growth in juvenile Florida pompano is at least 15.4 MJ/kg with a DP/DE between 23.8 and 25.1 mg/kJ. Florida pompano, Trachinotus carolinus, represents a small marine fishery in Florida with an estimated 227,000 kg total annual catch; however, because of its highly prized taste and texture, it continues to maintain a high market demand (McMaster et al. 2004). Florida pompano tolerate a wide range of salinities (Allen and Avault 1970), are resistant to low dissolved oxygen and handling stress, readily consume pelleted rations, successfully breed in captivity (Weirich and Riley 2007), and are an excellent candidate for aquaculture in a variety of systems (McMaster et al. 2004). However, little is known about the nutrient requirements of Florida pompano. Growth and efficiency of Florida pompano fed diets formulated for other species, typically trout feed with a 40% crude protein (CP), resulted in good growth and survival but poor feed efficiency (FE) (Watanabe 1995). As with many other marine species, Florida pompano are presumed to require high dietary CP. Lazo et al. (1998) feeding juvenile Florida pompano four isoenergetic diets (16.75 MJ/kg diet) with graded levels of CP determined that the minimum requirement was 45% CP; however, this was the highest concentration of CP fed. Lower FE reported for Florida pompano than some other marine species has been attributed to a high metabolic rate and poor digestibility (Tatum 1973; McMaster 1988; Lazo et al. 1998). Florida pompano are highly active, which suggests that previous diets may have had insufficient digestible energy (DE) to support metabolic and growth demands.When juvenile Florida pompanowere fed a diet (53%CP and 13% crude lipid [CL]) at various feeding frequencies, FEwas better than previously reported for Florida pompano; however, based on proximate analysis, Weirich et al. (2006) suggested that dietary energy was too high. Williams et al. (1985) fed juvenile Florida pompano four isonitrogenous diets formulated with 0–12%menhaden oil and determined that the optimum level offish oil in a 42% CP diet was between 4 and 8%, providing DE between 10.5 and 11.7 kJ/g diet and a digestible protein to digestible energy (DP/DE) ratio between 29.4 and 32.3 mg DP/ kJ DE. Identification of protein and energy requirements and determination of nutrient digestibility have reduced dietary CP requirements in some 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 40, No. 1 February, 2009 Copyright by the World Aquaculture Society 2009