Effects of taurine supplementation in a high-carbohydrate diet on growth performance, plasma biochemical, digestive and glucose metabolism enzymes in hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus)

Abstract

This study conducted an 8-week feeding trial to evaluate the effects of taurine supplementation in a high-carbohydrate diet on the growth performance, plasma biochemical indexes and glucose metabolism of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus). Six iso-nitrogenous (45.94 %) and iso-lipidic (8.71 %) diets were formulated containing 20 % carbohydrates (positive control group, PC) and 30 % carbohydrates (negative control group, NC), and were supplemented with 0.4 % (T1), 0.8 % (T2), 1.2 % (T3) of 1.6 % (T4) taurine on the basis of the PC diet. Five hundred forty fish (initial body weight 12.10 ± 0.30 g) were randomly distributed among the six treatments with triplicate groups of 30 fish in each treatment. The results showed that, compared with the PC, fish fed the NC diet significantly decreased the weight gain rate (WGR) and specific growth rate (SGR), the level of insulin-like growth factor-1 receptor (IGF-1R) in the liver, the activities of trypsin and α-amylase (AMS) in the intestine, and the activity of glucokinase (GK) in the liver. Under taurine supplementation, the highest significant values of WGR and SGR were found at the T3. The optimal taurine requirements in the 30 % carbohydrate diet were found to be 1.31 %, 1.31 % and 1.05 % based on WGR, SGR and feed coefficient rate (FCR), respectively. Compared with the NC, significantly higher activities of intestinal trypsin and AMS were found in the T1-T4. Hybrid grouper fed the T3 diet showed the significantly highest levels of plasma insulin and triglycerides. Significant increase in GK activity in the liver occurred under taurine supplementation above 0.8 %. Hepatocyte oil-red O and hematoxylin-eosin staining showed that 0.4 %∼1.2 % taurine supplementation could release hepatocyte fat deposition and maintain hepatocyte structure. Therefore, taurine enhances intestinal digestive function and regulates glycolipid metabolic to improve the utilization of dietary carbohydrates, thus promoting the growth of hybrid grouper.