The Study Of L-malic Acid On Nutritional And Physiological Effects Of Tilapia

L-malate which owns the pivotal role in the metabolism processs of organisms is the intermediate of tricarboxylic acid cycle (TCA) and its branch glyoxylate cycle. In order to provide the theory basis for the application of malate on tilapia forage, the preparation of acidifier and the use of acidifier as the alternative production for the green environment forage additive, and supply the important reference for the fish forage acidifier study in other fish, this experiment focus on the effects of malate on the Nutritional and Physiological of tilapia to get the increasing malate addition volume of young tilapia and discuss the growth-promoting mechanisms of malate on tilapia.We applied the single factor concentration gradient design and used the peru fish flour, meat flour, soybean and cottonseed grains in distilled liquor to prepare the basal ration to carry out the 56d growth experiment for 630 tail young tilapia (the initial weight were 31.76±0.04g), and we added malate to make seven groups of forage containing the same nitrogen ingredient whose final malate concentration were 0.0g/kg、0.5g/kg、1.0g/kg、2.0g/kg、4.0g/kg、8.0g/kg and 16.0g/kg, respectively. Every ration group were made three repetition of each containing 30 tail tilapia raising in the 0.38 m3 (0.32 m3 significant volume) fiberglass aquarium. The fishes were feed in the condition of 26-28 degrees water temperature, DO>6.0 mg/L, pH 6.5～7.0, ammonia nitrogen content<0.05mg/L, nitrite contents:0.009～0.020 mg/L. After the arrays, we researched the effects of malate on the growth properties, body shape, enteral nutrition (the gastrointestinal tract structure and the digestion enzyme activities) and the body immunity (the structure of hepatopancreas, immunity and the anti-oxidative indexs) of tilapia. The results were listed below:1. the effects of ration malate level on the feed acidity of tilapiaAs the increase of the malate, the acidness and the acidity were in a downtrend, and reached the lowest at 16.0g/kg group. We found that there were fine correlation between forage acidity and the addition level of malate. Took the addition level of malate (x) and the forage acidity (y) to proceed curve of second order analysis, we found the formula, y=0.0259x2-0.857x+22.164, R2=0.9789.2. the effects of ration malate level of the growth and body indexes of tilapiaAs the increase of the ration malate level, the weight growth rate and special weight growth rate of tilapia appeared to increase at earlier (0.0～1.0g/kg) and decrease at latter (1.0-8.0g/kg), then the rate at the 16.0g/kg group which was 18.62% and 8.68% higher than the control group increased suddenly and got the hightest. However, the forage coefficient was right opposite, reached the lowest at 16.0g/kg group which decreased 15.67% than control. There were no significant effects of ration malate on the body shape indexes ((CF and VIS) (P>0.05)3. the effects of ration malate level on the gastrointestinal digestion enzyme activities of tilapiaThe malate level added to the ration influenced the digestion enzymes obviously (P<0.05). The pepsin activities increased as the addition of the malate level of ration, and reached the topmost at 16g/kg group; The lipidase and amylase which were the highest at 1.0g/kg advanced firstly and fell down latter; The acid adding group was lower than control notably, but it was not significant among the acid adding group (P>0.05)4. the effects of ration malate on the H+-K+-ATP enzyme in stomach of tilapiaWith the advance of malate level in ration, the H+-K+-ATP enzyme in the tilapia stomach fell down earlier and upgraded latter, and was the lowest and the highest at 2.0g/kg and 16.0g/kg, respectively.5. The effecs of dietary malic acid on anti-oxidative function of tilapiaWith the increase of malimate, The MDA in sera of tilapia fell down earlier and raised latter, then the rate at 2.0g/kg which was 25.49% lower than the control group decreased lowest, the the lysozyme activities elevated first and fell down following, and was highest at 4.0g/kg. With the increase of malate in ration, the SOD in tilapia hepatopancreas raised earlier (0.0-1.0g/kg) and fell down latter (1.0-8.0g/kg); there were not significant differences among 2.0g/kg～8.0g/kg group, and the SOD reached the highest at 16g/kg;6. the effects of ration malate on the malic acid shutting enzyme (malic dehydrogenase and AST) activitiesWith the rise of ration malate, the activities of malic dehydrogenase and AST of tilapia hepatopancreas descent first and rised latter (0.0g/kg～8.0g/kg), when malate level reached 16.0g/kg, the malic dehydrogenase and AST activity were the highest,and 98.96%,42.20% higher than control partly.7. the effects of ration malate level on the structure of gastrointestinal and hepatopancreas of tilapiaWith the rise of ration malate, there were not pathological changes in the structure of gastrointestinal and hepatopancreas of tilapia and kept in a satifactory position. The optical micro-and scanning electron microscope observation showed that the thickness of gastric mucosa elevated first and fell down with the increase of ration malate, and the interval between gastric glands swelled, the permeability multiplied with the appearance of a layer of white membrance at the higher concentration. We used the optical microscope to observe the structures of intestines, and found that the length of intestinal villi assumed the raising and falling down manner with the increase of malate level, and reached the highest at lg/kg and 2g/kg. Our microexamination of the tissues of hepatopancreas showed that the structure of hepatopancreas kept perfectly.8. the effects of ration malate on the intestine flora of tilapiaThe intestinal tract bacillus bifidus numbers magnified with the increase of the ration malate level, while the pseudomonas which appeared the falling trend was in contrast.The results showed that:1. Optimal levels of malic acid content can enhance the rate of body weight gain, the specific growth rate and reduces the feed2. Optimum dietary levels of malic acid can improve the digestive enzyme activities of tilapia gastrointestinal tract and improve feed3. Appropriate levels of malic acid can improve the antioxidant and immune function of tilapia.4. Appropriate levels of malic acid can increase the intestinal villi length, mucosa thickness, and keep the structure of hepatopancreas from being damaged.5. Adding malic acid on tilapia has significant influence to intestinal flora, adding appropriate malic acid can increase the number of intestinal bacteria.6. In this study, 1.0g/kg of dietary malic acid content is appropriate to tilapia feed适宜...