Effects of intelligent feeding method on the growth, immunity and stress of juvenile Micropterus salmoides

The feeding method is of great significance for aquaculture production and cost. In recent years, research on intelligent feeding, a method based on fish appetite, has been trending. Few studies, however, have focused on fish welfare issues that can result from intelligent feeding. In this study, an adaptive feeder based on a practical intelligent feeding method was designed to evaluate whether this intelligent feeding method would impair fish welfare compared to traditional automatic feeding. The results indicated that the amount of residual feed and size inhomogeneity in the traditional group was significantly higher than that in the intelligent group. The results of the growth indicator showed that the weight gain rate (WGR) in the intelligent feeding group was significantly higher (30.17%) than in the traditional feeding group. Although no significant differences were observed in the survival rate (SR), the condition factor (CF) and the hepatosomatic index (HSI), the specific growth rate (SGR) in the intelligent feeding group was significantly increased by 8.33% while the feed conversion rate (FCR) was reduced by a remarkable 17.07% compared to the traditional feeding group. Moreover, intelligent feeding significantly improved the pepsin activity of the bass. In terms of immunity and antioxidant capacity, however, the fish in the intelligent feeding group had a significantly lower lysozyme (LZM) level than those fed with the traditional method. For superoxide dismutase (SOD), the intelligent group also displayed a lower activity value, although it was not significant. The intelligent feeding group had 0.14 nmol/mg protein higher malondialdehyde (MDA) activity than the traditional group. Regarding stress, although no statistical significance was observed, the cortisol level in the intelligent group was 1.9 ng/ml higher than in the traditional group. Together, these data suggested that the intelligent feeding method can significantly improve fish growth but may also result in stress and suppress innate immunity.