Effects of dietary organic acid supplementation on the growth, nutrient digestibility and intestinal histology of the giant grouper Epinephelus lanceolatus fed a diet with soybean meal

The purpose of this study was to evaluate the effects of dietary organic acid (butyrate and lactate) supplementation on the growth, nutrient digestibility and intestinal histology of the giant grouper Epinephelus lanceolatus that was fed a diet containing soybean meal. The diet that included soybean meal, which replaced 40% fish meal protein, was used as the control. One percent butyrate and lactate were added to the control diet to form the two experimental diets. Also, the all fish meal diet without organic acid was also included for comparison. A total of four experimental diets were each fed to three groups of giant grouper (initial wt: 17.37 +/- 0.18 g) in a recirculating rearing system for 8 weeks. After the growth trial, the nutrient digestibility by the fish was determined by using 0.5% chromic oxide as an inert indicator. The fish fed the all fish meal diet gained more (P < 0.05) weight than fish fed the control and the 1% lactate diets. The hepatic thiobarbituric acid reactive substance (TBARS) value was higher in the fish fed the control diet than that in other dietary treatments. Drymatter, lipid, copper (Cu), zinc (Zn), calcium(Ca) and phosphorus (P) digestibility were higher in fish fed the all fish meal diet, the 1% butyrate and lactate supplemented diets than the fish fed the control diet. The fish fed the control diet showed disordered lamina epithelialis and extended lamina propria comparing to the fish fed the all fish meal diet and 1% butyrate-diet. The results indicated that growth, nutrient digestibility and intestinal histology were adversely affected by replacement of the fish meal by soybean meal in giant grouper. The diet supplemented with 1% butyrate improved the negative effects excluding growth for the fish. Statement of relevance: To evaluate feed additives on growth, nutrient digestibility and intestinal histology of giant grouper fed diets with soybean meal. (C) 2016 Elsevier B.V. All rights reserved.