Influence of Green Tea Polyphenols on Feed Performance, Growth Performance, and Fish Body Component in Yellowtail (<i>Seriola quinqueradiata</i>)

Effects of green tea polyphenols (GTP), which contain (+)-catechin, (-)-epicatechin, (+)-gallocatechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate, on feed performance, growth performance and fish body component in the cultured fish were investigated. The moist pellets supplemented with different concentrations of GTP (0, 0.02 and 0.2%) were fed to young yellowtails (Seriola quinqueradiata) of 0 (zero)-year fish for 4 weeks. This experiment was performed repeatedly in culture farm. The total intake of feed, daily feed consumption, feed efficiency and feed gain ratio during whole test periods were observed for the evaluation of feed performance. On the 2nd and 4th week after feeding, length (fork length), body weight and visceral weight of the fish were measured, and then condition factor, ratio of visceral weight to body weight and daily gain ratio were calculated. Death of fish during whole test periods was also observed. The growth performance of fish was evaluated from these results. The content of moisture, protein, lipid, carbohydrate and ash in fish meat and viscera were analyzed on the 2nd and 4th week after feeding, and then the fish body components were calculated from these data. No remarkable changes in each feed performance index were observed among the all test groups. In the all test groups, no significant differences in the fork length, body weight, visceral weight, ratio of visceral weight to body weight, condition factor and mortality were observed, and the daily gain ratio was not also changed. However, fork length and body weight showed a tendency to be much increased in experiment 1 compared with experiment 2. It was speculated that this observation could be rationalized by higher water temperature of culture farm in the former than the latter. No changes in moisture, protein, lipid, carbohydrate and ash contents in fish meat and viscera were shown among three groups. Accordingly, it was suggested that GTP feeding showed no damages to feed performance, growth performance and body components of cultured fish. We have already reported that GTP feeding was effective to the suppression of oxidation of lipid, deterioration of flesh color and microbial growth, and also to the slow resolution after rigor mortis in fish body during round iced storage. It was concluded that GTP feeding would be useful for producing highly valuable cultured fish with safety and without decreasing upon the productivity from the results reported previously and this study.