Aquafin CRC - Southern Bluefin Tuna Aquaculture Subprogram: Application of the use of dietary supplements for improving flesh quality attributes of farmed SBT

Abstract

This research on the application of the use of dietary supplements for improving the flesh quality attributes of farmed SBT has been focused on improving the colour shelf life of the sashimi product. Previous outcomes of our research group (2001/248) and supporting data from associated CRC project groups have led to the current interest in evaluating the use of a supplementary feed for tuna farming that can be used to extend shelf life. Our previous research with SBT has examined the use of increased levels of dietary antioxidants to slow the browning process of tuna meat using fortified pellets and coated baitfish as a nutrient delivery system. We have established that feeding SBT pellets fortified with boosted levels of vitamins E and C and selenium will raise the level of these natural antioxidants in the fish muscle. Having demonstrated that higher levels of these antioxidants in the muscle consistently result in an extension of the colour shelf life of sashimi grade tuna meat; we also demonstrated that feeding SBT pellets fortified with a higher level of vitamin E alone is not as effective in extending the shelf life of SBT meat as a combination of higher levels of vitamins E and C. In addition, we found that pellet diets fortified with antioxidants are by far the most effective delivery system for these nutrients and therefore the most effective way to improve the shelf life of farmed SBT flesh. With that background research in place and the concurrent acceptance within the industry that additional antioxidant nutrients have a benefit the current project focused on gaining a better understanding of the application of available antioxidant nutrient and providing the industry will a reliable feed supplement to deliver additional nutrients to SBT. Within the current project the outcomes achieved have included the development and application of cell culture techniques through the adaptation of existing assays for oxidative stress from SBT muscle extracts and mammalian cell cultures to fish cultures. In this way the effects of simulated oxidative stress on SBT cell cultures and has enabled a close examination of oxidative stress processes at a cell level and identification of likely effective concentrations and combinations of novel antioxidants that combat this stress.