Taurine is an essential nutrient for yellowtail Seriola quinqueradiata fed non-fish meal diets based on soy protein concentrate

The requirement of dietary taurine in yellowtail fed a non-fish meal (FM) diet based on soy protein concentrate (SPC) was examined by a feeding trial. A recovery test (RCT) was also conducted to confirm the requirement of dietary taurine in yellowtail fed the SPC diet. The non-FM diet including 58% SPC as the protein source was supplemented with 0% (NTS) and 4.5% taurine (TS). A diet including 58% FM was also included as a reference. Juvenile fish (initial BW; 470 g) were fed one type of experimental diet for 39 weeks. The RCT group was fed the taurine un-supplemented SPC (NTS) diet for the first 23 weeks, and then fed the taurine supplemented SPC (TS) diet for 16 weeks. Tissue taurine concentration of the NTS group was significantly lower (P < 0.05) than that of the FM group. Specific growth rate (SGR) and feed conversion ratio (FCR) of the NTS group was significantly inferior compared to the FM group. In the NTS group, green liver syndrome was observed in all the samples. In contrast, tissue taurine concentration of the TS group increased to a similar level to that of the FM group. Compared to the NTS group, SGR and FCR of the TS group were significantly improved (P < 0.05) by taurine supplementation to the SPC diet. Moreover, yellowtail of this group could be reared for a long term without any physiological abnormalities, and their physiological condition and performance were comparable to the fish fed the FM diet. Although the physiological condition and performance of the RCT group was markedly inferior as the NTS group at the 23rd week (wk23) of the feeding trial, the physiological condition and performance of the RCT group markedly improved by the switch of the NTS diet to the TS diet at the end of feeding trial on the 39th week (wk39). These results indicate that yellowtail fed a non-FM diet based on SPC require taurine as an essential nutrient for maintaining normal physiological condition and growth performance.