Effects Of Acidifier And Phytase On The Physiological Responses Of Grass Carp, Ctenopharyngodon Idella

A detailed review of studying status on nutritional physiology of aquaculture feed additives were first introduced in this thesis, and then the studies on nutritional physiology of acidifiers in aquatic animals was undertaken. This study chose juvenile grass carp (Ctenopharyngodon idella) as experimental object to study the effect of different acidifiers on growth performance, digestive enzyme activity, antioxidation and non-specific immunity in order to discuss the mechanism of acidifier on grass carp. The current studies include the follows:(1) Effects of dietary different acidifiers on growth performance, digestive enzyme activity, antioxidation and non-specific immunity of grass carp, Ctenopharyngodon idella. (2) Effects of dietary acidifier and phytase on growth and phosphorus availability of grass carp, Ctenopharyngodon idella. The results are summarized as follows:(1) A 8-week feeding trial was conducted to investigate effects of different dietary acid supplements on growth performance,digestive enzyme activities,antioxidation and non-specific immunity of Ctenopharyngodon idellus(average body weight was about (10.33±0.03)g).5 test diets were applied for triplicate tanks and 30 fish was stocked randomly in each tank. No acid supplement was added in basal diet which was applied as control,0.21% of phosphoric acid, citric acid, lactic acid and composite acidifier were added in basal diet, respectively. The results showed that:①The results showed that the weight gain, specifc growth rate were significantly higher and the feed conversion rate was significantly lower in fish fed diet with citric acid, lactic acid and composite acidifier than those of fish fed basal diet(P<0.05), while no significant differernces were observed in fish fed diet with phosphoric acid(P>0.05).②No significant differences were observed in the whole body moisture, protein, lipid, ash and the contents of P、K、Na mineral elements (P>0.05). However, the contents of Ca, Mg, Fe, Mn and Zn mineral elements were significant higher in fish fed diet with composite acidifier than that of fish fed basal diet(P<0.05).③The activities of digestive enzyme of intestine and hepatopancreas in fish fed diets with composite acidifier were significantly higher than that of fish fed basal diet(P<0.05). Significantly higher activities of protease and amylase of intestine and hepatopancreas were observed in fish fed diet with citric acid than that of fish fed basal diet(P<0.05).④The serum activities of SOD and GSH-PX and LSZ in fish fed diets with different acidifiers were signifiantly higher than that of fish fed basal diet(P<0.05), while the activity of MDA was signifiantly lower in fish fed diets with composite acidifier(P<0.05). The activity of serum AKP in fish fed diets with different acidifiers was signifiantly improved(P<0.05). The results indicated that different acidifiers in fish feed diets could improve the growth performance, digestive enzyme activities, antioxidation and non-specific immunity. Accordingly, the feed efficiency of organic acid was better than mineral acid, and the feed efficiency in fish fed diets with composite acidifier was best.(2) This research was conducted to study the effects of dietary acidifier and phytase on growth and phosphorus availability of grass carp, Ctenopharyngodon idella. A 8-week feeding trial was conducted to investigate effects of different dietary acid supplements on growth performance.digestive enzyme activities,antioxidation and non-specific immunity of Ctenopharyngodon idellus (average body weight was about (10.33±0.03)g).3 test diets were applied for triplicate tanks and 30 fish was stocked randomly in each tank. No acid supplement was added in basal diet which was applied as control,0.21% of composite acidifier was added in basal diet as the diet acidifier, and 0.21% of composite acidifier and lOOOU/Kg phytase were added in basal diet as the diet phytase. The results showed that:①The weight gain, specifc growth rate were significantly higher and the feed conversion rate was significantly lower in fish fed diet with composite acidifier and phytase than those of fish fed basal diet(P<0.05), and the diet phytase was the best.②No significant differences were observed in the whole body moisture, protein, lipid, ash and the contents of P、K、Na mineral elements (P>0.05). However, the contents of Ca. Mg, Fe, Mn and Zn mineral elements were significant higher in fish fed diet with composite acidifier and phytase than that of fish fed basal diet(P<0.05). There was significant differences observed in the body index.③Grass carp fed diet supplemented with composite acidifier and phytase had significantly antioxidation and non-specific immunity.④The phosphorus availability was both significant improved in the diet acidifier and phytase, the results indicated that the growth and phosphorus availability together with acidifier and phytase.