Variance Analysis of Intestinal Microbial Diversity of the Noble Scallop (Chlamys nobilis) under Enrofloxacin Exposure

Abstract

This study was aimed to evaluate the effects of feeding frequency on growth performance, antioxidant status and immunity of juvenile red swamp crayfish Procambarus clarkia (average weight: 3.01±0.02 g). Crayfish were randomly assigned to one of five feeding frequencies (1,2,3,4 and 5 times/day, F1, F2, F3, F4 and F5) following the same ration size for 60 days. After the feeding trial, fish were challenged with white spot syndrome virus (WSSV) and cumulative mortality was recorded for the next 4 days. The results showed that the weight gain rate (WGR) of crayfish tended to increase initially and then decrease as feeding frequency increased. The WGR in F3 were significantly higher than those fed 1, 4 and 5 times/ day (P<0.05). The highest serum lysozyme (LZM), lowest catalase (CAT) and malondialdehyde (MDA) were observed in crayfish fed 3 times/day. However, there were no significant differences in cortisol, glucose (Glu), and superoxide dismutase (SOD) among all groups (P>0.05). The cumulative mortality in F3 was significantly lower than that of the other groups at d4 after challenge (P<0.05). In conclusion, both low and high feeding frequencies could cause stress of juvenile Procambarus clarkia and the optimal feeding frequency to enhance growth and immunity of this species at juvenile stage is 3 times/day.