Effects of riboflavin on growth performance, body composition, immunity and antioxidant capacity of Schizothorax prenanti

The purpose of the experiment was to explore the effects of different riboflavin levels on the growth performance, body composition, and immune parameters of Schizothorax prenanti. Six purified diets were formulated to contain 0.67、2.96、5.83、9.05、11.58 and 23.42 mg/kg riboflavin, respectively. S. prenanti with an average initial body weight of (10.54±0.01) g were fed the diets for 8 weeks and each diet had 3 replicates with 30 fish per replicate．The results showed as follows: the weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) of the fish increased first and then decreased with the increase of riboflavin level, and reached the maximum and significantly higher in the 5.83 mg/kg group than those of the other groups; the feed coefficient ratio (FCR) decreased first and then increased, the lowest in the 5.83 mg/kg group and significantly lower than the other groups; riboflavin significantly affected the survival rate of the test fish (SR), liver index (HSI) and visceral index (VSI); riboflavin significantly affected the crude fat content of whole fish, but had no significant effect on crude protein, moisture and ash content. The amount of riboflavin in the liver increased with the increase of the riboflavin level; the liver D-α-amino oxidase (DAAO) activity reached the highest in the 5.83 mg/kg group. The activities of serum lysozyme (LYZ) and catalase (CAT) increased first and then stabilized with the increase of riboflavin. The content of malondialdehyde (MDA) decreased first and then stabilized with the increase of riboflavin level. It indicated that riboflavin can effectively improve the digestibility of feed, improve the immunity and antioxidant capacity, and promote its growth. Considering the best growth performance and immune ability of S. prenanti, 5.32-5.89 mg/kg of riboflavin would be the suitable level.