POTENTIAL RISKS OF HIGH LEVEL REPLACEMENT OF DIETARY FISH MEAL BY CANOLA MEAL ON LARGE YELLOW CROAKER LARIMICHTHYS CROCEA (RICHARDSON, 1846): GROWTH, HEALTH AND NUTRITIONAL VALUES AS A FOOD FISH

A growth trial was conducted to evaluate the potential risks of high levels replacement of dietary fish meal by canola meal on large yellow croaker Larimichthys crocea (Richardson, 1846). It focused on the growth, health and nutritional values as a food fish. Diet with 60% of fish meal was formulated as the control group (FM). The other four experimental diets were formulated with graded replacement levels of fish meal by canola meal according to mass fraction. These replacement levels included 15% (CM15), 30% (CM30), 60% (CM60) and 100% (CM100), respectively. The 5 experimental diets were fed to 5 groups of large yellow croakerinitial weight of (135.38±1.02) g for 12 weeks. There were 5 replicates per group. Results showed that the growth and feed conversion ratio (FCR) of large yellow croaker was not significantly influenced when the replacement level of dietary fish meal by canola meal were 15% and 30%. However, values of final body weight and the specific growth rate significantly decreased and value of FCR significantly increased in groups of CM60 and CM100 (P < 0.05). Feed intake increased significantly, while condition factor significantly decreased in CM100 group (P < 0.05). Histologically, less twist and disorganized morphology in intestine, distinct circular vacuoles and nuclear perturbations in liver were found when fish was fed with canola meal included diets. Through the digital X-ray analysis of skeleton, both vertebral body and mouth deformities were found in fish fed with canola meal. As for nutritional values, no significant difference was observed in lipid content, protein content and amino acid profile of dorsal muscle. While fatty acid compositions were significantly changed in muscle. N-6 fatty acid contents significantly increased, and DHA and EPA contents decreased (P < 0.05). Based on the standards of the European Food Safety Authority (EFSA), however, these changes didn't influence the fact that large yellow croaker was also recommended as a healthy food fish. In summary, the negative impacts of high levels (60% and 100%) replacement of dietary fish meal by canola meal on large yellow croaker mainly related to the reduced growth performances, altered intestinal and hepatic morphology as well as impaired skeletal health. However, large yellow croaker fed with canola meal in diets still meet the standard of healthy food, thus canola meal replacement didn't significantly influence the nutritional value of large yellow croaker as a food fish.