GROWTH AND PROXIMATE COMPOSITION OF SEA-REARED RAINBOW TROUT (Onchorynchus mykiss) FED WITH ASCIDIAN (Halocynthia roretzi) TUNIC CAROTENOIDS AND CONJUGATED LINOLEIC ACID (CLA)
CLA is widely used to reduce body fat mass. However, free CLA was known to induce inflammatory respond to animals. To this date, there have been numerous experiments on incorporation CLA to fish. These studies indicated that the abilities of fish incorporated CLA into muscle were vary from species to species. Moreover, the dietary CLA higher than 2% would affect fish growth negatively. Meanwhile, carotenoids are well known as feed attractant and have many positive effects such as enhance muscle colorization, antioxidant, and anticancer. Sea squirt (Halocynthia roretzi) tunics are by-product of sea squirt seafood production. This seafood is very popular in Korea with production capacity reached 7,038 tons in 2014 and projected to reach 9,977 tons in 2015. The tunics contain high amount of carotenoid and other nutritious substances.
In this study, sea-rearing of rainbow trout was carried out for 90 days in Tongyeong sea area, Korea. Control group (CN) were given basal diet feed (Aler Silver™) which had already contain 40 mg.kg-1 astaxanthin and CLX were given basal diet with inclusion of 3% CLA coupled with 10 mg.kg-1 of H. roretzi tunic carotenoids extract.
Result revealed that after 60 days of treatment CLX weight was slightly higher (Table 1) with apparent enhancement of muscle colorization for CLX (Figure 1). These data revealed that the negative effect of CLA to rainbow trout growth was unobserved.
The proximate composition of CN was 71.7±2.0%, 15.7±2.3%, 11.7±0.6%, and 0.9±0.1% for moisture, protein, lipid and ash content respectively. On the other hand the moisture, protein, lipid, and ash content of CLX were 69.3±0.6%, 17.5±0.6%, 12.3±0.6%, and 0.9±0.0% respectively. These results indicated that 3% dietary CLA coupled with carotenoid extract from ascidian (H. roretzi) tunics could positively enhance the weight and proximate composition of sea-reared rainbow trout.