Improving Plant-based Diets for Florida Pompano, Trachinotus carolinus.

Abstract

Florida pompano aquaculture is a growing enterprise in the United States and production is increasing. Success of Florida pompano production is dependent on the supply of cost-effective diets that promote optimal growth and contain alternative plant proteins as the primary protein sources with reduced dependence on fishmeal. However, increased inclusion of plant protein sources in diets presents problems such as anti-nutritional factors, non-starch polysaccharides and imbalanced amino acid profiles. In order to increase digestion of plant proteins, supplemental carbohydrase and improvements in amino acid profiles can provide solutions. To facilitate the development of sustainable and cost-effective diets for Florida pompano, two studies evaluating dietary lysine requirement and supplementation of commercial carbohydrase enzymes endo-1,4- ß-xylanase and endo-1,4-ß-glucanase in plant-based diets was conducted. In the first study, an experimental growth trial was conducted where a combined eight diets (40% protein and 8% lipid) were formulated with graded levels of lysine (1.42-2.43% DM) and fed to juvenile pompano. The second research trial was conducted with iso-nitrogenous (40%) and iso-lipidic (8%) test diets containing 0, 0.015, 0.030, and 0.045% of commercial carbohydrase enzymes endo-1,4-ß-xylanase and endo-1,4-ß-glucanase. Results from the lysine work indicated significant differences in final weight, percent weight gain (PWG), thermal growth coefficient (TGC) and feed conversion ratio between fish reared on the basal diet and the rest of the experimental diets. Survival was variable among all treatments and significant differences existed between pompano fed the 2.12 and 1.57% lysine diets. No significant differences were observed in whole body proximate compositions of fish, but significant differences were observed in a few of the amino acid levels of whole fish including: aspartic acid, glutamic acid, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tyrosine and valine. The 4-parameter saturation kinetic model was used to model TGC to determine the dietary lysine requirement. A quantitative lysine requirement was determined to be 1.67% of the dry diet. In the second experimental trial, no significant effects of dietary enzyme supplements were found for initial growth, final growth, PWG, FCR, feed intake, survival (%), apparent net protein retention (ANPR) and apparent net energy retention (ANER). However, TGC was significantly higher in fish fed the 0.015% carbohydrase diet compared to the 0.030% carbohydrase diet. Additionally, no significant differences were identified in mean apparent digestibility of dry matter (ADDM) and apparent digestibility of energy (ADE). The diet supplemented with 0.030% carbohydrase had significantly higher mean apparent digestibility of protein (ADP) compared to the basal diet without supplement. An additional 3.37% protein on the basis of digestible protein was available to Florida pompano fed experimental diets containing any amount of carbohydrase. Based on the results from the two growth trials, Florida pompano fed plant-based diets require a small amount of lysine (1.67%, dry weight) and commercial carbohydrase (0.015%) to optimize growth, feed utilization and protein digestibility.