Tolerance Study On Ethoxyquin And Tertiary-butylhydroquinone In Largemouth Bass (Micropterus Salmoides)

This study was conducted to investigate the tolerance of largemouth bass (Micropterus salmoides) on ethoxyquin (EQ) and tertiary-butylhydroquinone (TBHQ) on the growth performance, antioxidant response and histopathology. On basis of the above studies, the further study was aimed to investigate the tolerance and safety margin in largemouth bass. The results and conclusions are summarized as follows1. A tolerance study on ethoxyquin in laegemouth bassA 10-week growth trial was conducted to evaluate the tolerance of largemouth bass on EQ based on the growth performance, antioxidant response and histopathology. Four experimental diets were prepared with EQ levels at 0 (FFO),150 (FFO-150),300 (FFO-300) and 1500 (FFO-1500) mg/kg. in which 150 mg/kg was the maximum recommended levels.300 and 1500 mg/kg were 2 and 10 fold levels, respectively. Each diet was fed to six replicates with 30 largemouth bass (initial body weight= 4.01±0.01 g). In addition, a negative control (OFO) with 7% oxidized fish oil was designed. The fish of OFO group showed the lowest growth performance, and no significant difference was observed in other groups (.P>0.05). Diet included with 300 and 1500 mg/kg EQ improved the survival. The highest level of EQ (1500 mg/kg) significantly increased hepatosomatic index (HSI) and viscerasomatic index (VSI) (P<0.05). the condition factor (CF) of FFO-300 was significantly higher than that of OFO group (P<0.05). The addition of EQ significantly decreased glutathione S-transferase (GST) in liver (P<0.05). EQ enhanced superoxide dismutase (SOD) and total antioxidative capability (T-AOC) significantly in muscle(P<0.05). Antioxidant enzymes of each group changed erratically in gill. CAT and T-AOC were decreased with higher EQ levels significantly in heart (P<0.05). Malondiadehyde (MDA) contents were decreased with higher EQ inclusion levels in each tissues (P<0.05). Different degrees of liver histological damage were observed in every group, and fish fed diets with 150 and 1500 mg/kg EQ relieved the symptom. Meanwhile EQ didn’t cause negative effects on distal intestines. The present study showed that the 150mg/kg EQ had a positive effect on antioxidant and it was safe when utilized as antioxidant in fish feed. The 10 fold of safety margin was obtained by the present study.2. A tolerance study on tertiary-butylhydroquinone of largemouth bassA 10-week growth trial was conducted to evaluate the tolerance of largemouth bass on TBHQ based on the growth performance, antioxidant response and histopathology. Four experimental diets were prepared with TBHQ levels at 0 (FFO). 200 (FFO-200),400 (FFO-400) and 2000 (FFO-2000) mg/kg. in which 200 mg/kg was the maximum recommended levels.400 and 2000 mg/kg were 2 and 10 fold levels, respectively. Each diet was fed to six replicates with 30 largemouth bass (initial body weight= 4.01 ±0.01 g). In addition, a negative control (OFO) with 7% oxidized fish oil was designed. Compared with the FFO group, the growth performance of fish was improved by the supplementation of 200 and 400 mg/kg TBHQ in the diet but suppressed by 2000 mg/kg dietary TBHQ (P>0.05). This resulted in a significant decrease in the growth of fish from the FFO-2000 group compared with the other treated groups (P<0.05). The condition factor (CF). hepatosomatic index (HSI) and viscerasomatic index (VSI of ish from FFO-400 and FFO-2000 group were significantly higher than that of the fish from the OFO group (P<0.05). The addition of TBHQ significantly decreased the activity of glutathione S-transferase (GST) in the liver (P<0.05). Meanwhile, the supplementation of 2000 mg/kg TBHQ in the diet significantly increased the activity of superoxide dismutase (SOD) and catalase (CAT) in the muscle (P<0.05). The MDA content in the gill was highest in the OFO group (P<0.05) and it was reduced by the inclusion of TBHQ in the diet (P>0.05). Hepatic lesions were observed across all the experimental groups with some amelioration of the liver damage detected in the FFO-200 group. Negative effects were also detected in the distal intestine of fish from the OFO and FFO-2000 group. The present study showed that 200 mg/kg TBHQ was safe to be included in the diet of laraemouth bass and a 2-fold safety margin was obtained.