Effects of Dietary Schizochytrium on the Growth Performance, Serum Nonspecific Immunity Indices, and Disease Resistance of Cyprinus carpio var. Jian

Abstract:

Five hundred and forty Cyprinus carpio var. Jian with initial body weight of (26.77±1.56) g were randomly divided into 6 groups, and every group had three replicates each of which had 30 fish. Six diets were formulated with Schizochytrium at the concentrations of 0, 0.40%, 0.80%, 1.20%, 1.60% and 2.00%. An 8-week feeding trial was conducted to determine the effects of diary Schizochytrium on growth performance, serum nonspecific immunity indices, and disease resistance of C. carpio Jian. The results showed that weight gain rate and specific growth rate significantly increased in the 0.80% group (P<0.05). The highest condition factor was observed in the 1.20% group (P<0.05). The survival rate showed no significant difference between the six groups (P>0.05). The antioxidant and nonspecific immune activities were apparently altered by Schizochytrium (P<0.05). As the concentration of Schizochytrium increased, the contents of catalase, total superoxide dismutase, and glutathione were first elevated and then reduced, and the maximum of each was observed in the 1.20%, 0.80%, and 1.20% groups respectively (P<0.05). The malondialdehyde content dropped first and then increased with the lowest value observed in the 0.8% group. The nonspecific immune capacity in the 0.80% group was significantly higher than in other groups (P<0.05). The activity of lysozyme was raised and then reduced along with the increase in the Schizochytrium level, and the maximum was observed in the 1.20% group (P<0.05). The nitric oxide content rose along with the rise of Schizochytrium level, and was significantly higher than the control group (P<0.05). The Aspartate aminotransferase/aspartate aminotransferase (GOT/GPT) ratio reached the minimum in the 0.80% group. Also in the 0.80% group, the respiratory burst activity of blood cells was elevated significantly and the accumulated mortality rate was the lowest (P<0.0.5). In conclusion, we recommended that the optimal Schizochytrium level for C. carpio Jian should be 0.80%–1.20%.