Growth, survival and immune responses of juvenile common carp Cyprinus carpio fed with diets enriched with α- tocopheryl acetate
Cyprinus carpio is a popular food fish species and is stocked regularly in reservoirs of Sri Lanka. However in semi-intensive aquaculture, growth and survival of this species are very low resulting in high production cost. The present study was carried out to determine the growth, survival and immune enhancement to pathogenic Aeromonas hydrophyla of juvenile common carp fed with tocopheryl acetate augmented formulated feed. Experimental set up included four treatments each with three replicates arranged in completely randomized design. Initial total weight of the experimental individuals ranged from 200 to 320 g. Experimental fish, which were stocked in 150 cm x 150 cm x 60 cm cement tanks were fed twice a day. The four treatments were; non-enriched commercial feed (T1), non-enriched formulated feed (T2), formulated feed enriched with Tocopheryl Acetate (TA) 2 mg (T3) and formulated ration enriched with TA 4 mg (T4). After the end of the feed trial, experimental animals were exposed to 5 ppm A. hydrophila concentration for 5 minutes duration. The highest Specific Growth Rate (SGR) (1.21) was observed in treatment T4, followed by Control treatment T1 (1.16), which were not significantly different from T3 (1.11). The lowest SGR (1.04) was recorded for T2. The highest (93%) and the lowest (69%) survival were observed in T4 and T3 respectively. The lowest Food Conversion Ratio (FCR) (1.61) was also observed in T4. In T3 and control, they were 1.93 and 1.96 respectively. The highest FCR was also observed in T2 (2.14). No mortality was recorded in T4 after exposing to bacteria concentration while it was 20% in T3. The highest percentage mortality (60%) was recorded from T2 followed by the control (40%). Results indicate that enrichment of prepared feed using Tocopheryl Acetate gives a good growth rate, good survival, hence reducing the production cost. Further, results indicate that Tocopheryl Acetate positively enhances the immunity of the experimental fishes to Aeromonas infection.