| This study was conducted to investigate the tolerance of largemouth bass(Micropterus salmoides) on Butyl-hydroxyanisole(BHA), Butylated hydroxytoluene(BHT)and various selenium sources on the growth performance,biochemical indexes, antioxidant response and histology of liver and intestine. 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 follows: 1. Tolerance of Butyl-hydroxyanisole in Diets of Largemouth Bass(Micropterus salmoides)A 10-week growth trail was conducted to evaluate the tolerance of largemouth bass(Micropterus salmoides) on Butyl-hydroxyanisole(BHA) based on growth performance,biochemical indexes,hematological and tissues antioxidant response, and histology of liver and intestine. Four experimental diets were prepared with BHA supplement levels at 0(D0), 150(D150), 300(D300) and 1500(D1500) mg/kg, in which D150 was designed as the maximum recommended level, otherwise the D300 and D1500 were 2 and 10 fold levels of D150, respectively. Each diet was fed to 6 replicates with 30 largemouth bass initial body weight[(6.20±0.01g)] in each tank. The results showed that: fish in D150 group showed the highest growth performance(P<0.05), and no significant differences were observed in other groups(P>0.05). The condition factor, hepatosomatic index and viscerasomatic index in all groups had no significant differences(P>0.05). Plasma total cholesterol(TC), triglyceride(TG) and alkaline phosphatase(AKP) contents in D150 group were significantly higher than those of other groups(P<0.05). The ratio of HDL-C/TC in D150 and D300 groups was significantly higher than that in D0 and D1500 groups(P<0.05). Plasma AST and ALT activity in D1500 group was significantly lower than those of D0 group(P<0.05). Hepatic SOD activity in D150 and D300 groups was significantly lower than that in D0 group(P<0.05). 1500mg/kg BHA inclusion could significantly enhance the hepatic T-AOC, and MDA content in plasma, heart and liver were significantly decreased in each BHA inclusion groups.Different degrees of liver and intestinal histological damage were observed in D0, D150 and D1500 groups, but fish fed diets with 150 and 1500mg/kg BHA relieved the symptom. The present study shows that the 150mg/kg BHA could enhance the fat metabolism and antioxidant response of of largemouth bass, and a 10 fold of safety margin is obtained in the present study. 2. Tolerance of Butylated hydroxytoluenein Diets of Largemouth Bass(Micropterussalmoides)A 10-week growth trail was conducted to evaluate the tolerance of largemouth bass(Micropterus salmoides) on Butylated hydroxytoluene(BHT) based on growth performance,biochemical indexes,hematological and tissues antioxidant response, and histology of liver and intestine. Four experimental diets were prepared with BHT supplement levels at 0(D0), 150(D150), 300(D300) and 1500(D1500) mg/kg, in which D150 was designed as the maximum recommended level, otherwise the D300 and D1500 were 2 and 10 fold levels of D150, respectively. Each diet was fed to 6 replicates with 30 largemouth bass initial body weight[(6.20±0.01g)] in each tank. The results showed that:fish in D150 group showed the lowest feedefficiency ratio(P<0.05). Thecondition factor(CF) of D150 and D300 groups was significantly higher than that of D1500 groups(P<0.05). The hepatosomatic index(HSI) and viscerasomatic index(VSI) in D150 group were significantly higher than those of D300 groups(P<0.05).Plasma total cholesterol(TC), triglyceride(TG), alanine aminotransferase(ALT) and alkaline phosphatase(AKP) contents were significantly decreased in each BHTinclusion groups(P<0.05). Heart superoxide dismutase(SOD) activity was significantly enhanced by BHT supplementation(P<0.05).Total antioxidative capability(T-AOC) in liver, muscle and heart was significantly enhanced with BHT supplemental level increasing(P<0.05). Malondiadehyde(MDA) content in muscle, heart and plasma was significantly decreased in each BHTinclusion groups(P<0.05). 300mg/kg BHTinclusion could significantly enhance the plasmatic catalase(CAT) activity(P<0.05), and heart CAT activity in D1500 group was highest(P<0.05). Plasmaglutathione peroxidase(GPx) activity was significantly enhanced in each BHTinclusion groups(P<0.05).Different degrees of liver histological damage were observed in each group, but fish fed diets with 150 and 1500mg/kg BHT relieved the symptom. The present study shows that the 150mg/kg BHTcould enhance the fat metabolism and antioxidant response of of largemouth bass, and a 10 fold of safety margin was obtained in the present study. 3. Tolerance of Various Selenium Sourcesin Diets of Largemouth Bass(Micropterussalmoides)A 10-week growth trail was conducted to evaluate the tolerance of largemouth bass(Micropterus salmoides) on various selenium sources based on growth performance, biochemical indexes,hematological and tissues antioxidant response. Each diet was fed to 4 replicates with 20 largemouth bass initial body weight[(13.00±0.02g)] in each tank. We use a typical commercial basal diet in the trial, in which the basal Se level was 0.7mg/kg, it had been up to the grade of the HRL of MOA(0.5mg/kg). Based on the formulation, we designed two lipids sources of fresh fish oil and oxidized fish oil as a control(FC) and a negative control(OC). Based on FC and OC, six diets with 0.5mg/kg of Se from Na2 Se O3, Se-Yeast and a premix of Na2 Se O3 and Se-Yeast were prepared and named as FI2, OI2, FY2, OY2, FM2 and OM2. Besides we designed a 3-fold of HRL Se(added 1.0mg/kg of Se) based on the OC for the tolerance test of three target stuffs, which are named as OI3, OY3 and OM3, respectively. The Three-way ANOVA showed that: growth performance in oxidized fish oil group was significantly higher than those of fresh fish oil group(P<0.05). Selenium sources and selenium levels had no significant differences on growth performance of largemouth bass(P>0.05). Selenium sources had no significant differences on the tissues antioxidant response of largemouth bass(P>0.05). Decreased antioxidant capacity, oxidative damage, distal intestinal damage and inflammatory response were observed in 3-fold group. OY2 and OM2 groups could significantly enhance growth performance and relieve oxidative stress of largemouth bass. According to the results of growth performance, physiological and histopathologic response, 0.5mg/kg Se(basal Se level) could meet the need of largemouth bass in the low degree oxidation of feed. However, requirement of Se is relatively improved in the high degree oxidation of feed.2 fold-group could relieve largemouth bass from the oxidative damage.Se-Yeast and Se-Mix were relatively more effective than Na2 Se O3, and further improvement of selenium levels(3 fold-group) was not safe in aqua-feeds. |
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