Taurine supplementation and palm oil substitution in low-fish meal diets for young yellowtail Seriola quinqueradiata

Abstract

The effects of taurine supplementation and palm oil replacement in a low-fish meal (FM) diet for yellowtail (Seriola quinqueradiata) were examined in a feeding experiment using four different diets. The control diet had an FM content of 600 g/kg (FM60). The low-FM diets contained 350 g/kg FM, 170 g/kg corn gluten meal, and 170 g/kg defatted soybean meal (FM35). Taurine was supplemented in FM35 at 7.5 g/kg (FM35T). Fish oil in the FM35T diet was replaced with palm oil (FM35TPO). Juvenile fish (initial body weight 236 g) were fed these diets for 36 weeks. The mean body weight and specific growth rate were not significantly different among the treatments until 24 weeks (week 24). However, they were significantly higher in FM35T-fed fish compared with FM35-fed fish at week 36. The feed intake levels of FM35- and FM35T-fed fish were comparable or higher than that of FM60-fed fish whereas the intake levels of FM35TPO-fed fish were always significantly higher than those of FM60- and FM35T-fed fish (P < 0.05). The tissue taurine concentrations of FM35-fed fish were significantly lower than those of FM60-, FM35T-, or FM35TPO-fed fish in all tissues examined at all sampling times (P < 0.05). Taurine supplementation is necessary for reducing the dietary FM content for yellowtail over long feeding periods. FM35TPO-fed fish were leaner than FM35T-fed fish, as evident from the lower lipid concentration in the muscles and whole body. The lower feed conversion ratio of FM35TPO-fed fish compared with FM35T-fed fish suggested that the lower lipid absorption from the FM35TPO diet was due to the inclusion of palm oil. Despite the economic advantage of palm oil compared with fish oil, use of palm oil should be limited because it has lower digestibility in cold water conditions.