TOLERANCE AND EFFICACY OF CYSTEAMINE HYDROCHLORIDE IN THE DIETS OF LARGEMOUTH BASS (MICROPTERUS SALMOIDES)

The effects of dietary cysteamine hydrochloride (CSH) on growth performance, hematology and histopathology of liver and intestine of largemouth bass (Micropterus salmoides) were conducted for safety assessment of CSH in fish diet. The CSH was designed at levels of 0, 108, 324, 648 and 32400mg/kg diet respectively. The highest dose group was 100 times higher than optimum. The control diet had inclusion with 38.93% crude protein, 9.82% crude fat and 18.86 MJ/kg gross energy. Each diet was fed to triplicate groups of the experimental fish initial body weight was (14.25?.1)g rearing in a re-circulating system for 8 weeks. The experimental fish were fed twice daily and at the start and end of the experiment, the fish were starved for 24h and batch weighed. Results showed that special growth rate, feed intake and the activity of pepsase, trypsinase in intestine of fish fed diet with 648mg/kg CSH level were significantly higher than those of control group. However, feed conversion ratio, survival, hematological indexes and amylase activity in intestine did not show significant difference from those of control and lower CSH inclusion level groups. In the highest concentration (32400mg/kg), the growth performance, survival and the activity of pepsase, trypsinase of fish were decreased significantly. The frequency of pyknosis in liver and abnormal symptom of intestine in fish fed 648mg/kg diet were observed. Accordingly, the NOAEL of tested additive (including 27% CSH) in the diets of largemouth bass was 24 mg/kg穡穌. The NOAEL of CSH in the diets of largemouth bass was 6.5 mg/kg穡穌.