Dietary branched-chain amino acid supplementation affects growth and hepatic insulin-like growth factor gene expression in yellowtail,Seriola quinqueradiata

Abstract

We investigated the effect of dietary supplementation with a branched-chain amino acid (BCAA) mixture (valine, leucine and isoleucine) on juvenile yellowtail (Seriola quinqueradiata) growth and hepatic insulin-like growth factor (IGF) gene expression. Total dietary BCAA content was 8.1, 8.5, 9.0 and 9.8 g kg−1 for the control, 0.4%, 1.0% and 2.0% BCAA experimental groups, respectively. Body weight was measured on day 77, after which fish were fasted for 3 days and refed; the livers were then removed 3 or 9 h later for analysis of hepatic gene expression. Body weight significantly increased in the BCAA-supplemented groups. Hepatic expression of IGF1 and IGF2 significantly increased in the 2% BCAA group at 3 and 9 h after refeeding. In the 1% BCAA group, hepatic IGF1 expression tended to be higher at 9 h than in the control group after refeeding. Also, hepatic IGF2 significantly increased at only 9 h after refeeding in the 1% BCAA group. In conclusion, dietary supplementation with crystalline BCAAs increased growth and hepatic expression of IGF1 and IGF2. These results suggest that dietary crystalline BCAA supplementation would be a valuable addition to yellowtail aquaculture practices.