Effects of various levels of squid hydrolysate and squid meal supplementation with enzyme-treated soy on growth performance, body composition, serum biochemistry and histology of Florida pompano Trachinotus carolinus

Abstract

The purpose of this study was to evaluate the impact of plant-based diets supplemented with various levels of enzyme-treated soybean meal (ESBM) and squid products on the growth, proximate composition, serum biochemistry, and liver and intestinal histological alterations in pompano (Trachinotus carolinus). A 15% poultry by-product meal (PBM) based practical diet was used as a reference and basal diet was produced by replacing PBM with ESBM. Basal diet was then modified to contain varying levels of squid products. Squid hydrolysate (SH) and squid meal (SM) were added to basal diets, to produce diets containing 1, 2 and 4% of the squid products. A total of eight experimental diets were each fed to quadruplicate groups of 20 pompanos (mean initial wt=7.68±0.1g) in a recirculating rearing system for 56d. Results from the growth trial indicate that fish fed with basal diet exhibited significantly lower growth performance and feed utilization as compared to fish fed with PBM. The addition of 4% SH improved the response of basal diet and did not show any significant difference in terms of growth performance as compared to PBM. Whole body proximate and amino acids composition of fish were not significantly different among fish reared on any of the diets. Data on mineral composition of fish showed that the content of phosphorus and calcium were significantly higher in fish fed with basal diet compared to other treatments. Total protein and cholesterol level of fish fed PBM were significantly lower compared to basal diet. Total albumin, alanine transaminase, aspartate transaminase, and bile acids were similar among the dietary treatments. Fish fed with basal diet showed disordered vacuolization in the liver and decreased the lamina propria thickness in the intestine. The inclusion of 4% SH partly prevented the alteration of liver and distal intestine of Florida pompano and findings were similar to fish fed with PBM. Based on these results, combination of ESBM and 4% SH has the potential to serve as an alternative protein source and attractant to improve the efficacy of plant-based diet for pompano.