Studies Of α-Ketoglutarate On Alleviating Ammonia Nitrogen Stress Of Ctenopharyngodon Idellus

Ammonia nitrogen in water directly affects the production of aquaculture breeding. Conflicted with the problem how to degraded the ammonia nitrogen in water, we studied the effects of a-Ketoglutarate on alleviating ammonia nitrogen stress of Grass Carp from the nutritional point in order to provide guidance for the application of AKG as anti-ammonia stress feed additive. Results are as bellow:One:The safe ammonia nitrogen concentration of Grass Carp:The research studied the toxic experiment of ammonia-N on juvenile Grass Carp which initial weight was 11.0±0.4 g and the water temperature was 33±1℃, pH was 7.2±0.1, dissolved oxygen content was over 5.0 mg/L.The results showed that the toxicity were significant positive correlation between the ammonia-nitrtie and maintained time. The 24、48、72 and 96h median lethal concentration of molecular ammonia were 1.15、0.85、0.68、0.47mg/L, and the safe concentration was 0.047mg/L. The 24、48、72 and 96h median lethal concentration of total ammonia-nitrtie were 74.90、55.36、 44.29 and 30.61 mg/L, respectively, and the safe concentration was 3.06 mg/L.Two:The Grass Carp was selected to evaluate the change of blood ammonia and the expression level of Rhcg2, Rhag mRNA at different time points of ammonia nitrogen stress. The Grass Carp with an average body weight of 11.8±0.5 g were exposed to molecular ammonia level at 0.35mg/L. The results showed that:(1) The blood ammonia level showed a trend of rising and reach its peak at 12 h (P<0.01), then it declined to its lowest at 48h (P<0.01) and rise again at 96h. (2) The expression level of Rhcg2 and Rhag mRNA showed a trend of rising in brain, spleen, intestinal and kidney after exposed to ammonia, they are significant higher (P<0.01 or P<0.05, respectively) than the control group at 24h. It showed a declined trend after 24h, and rised again in gill and instetinal at 96 h, significant higher than the control groups (P<0.01). When the Grass Carp blood ammonia concentration is high at 24h and under a lot of stress, the expression quantity of Rhcg2 and Rhag mRNA were largest. These results showed that:when the blood ammonia concentration is too high, the body to alleviate the injury by improving Rhcg2. Rhag transport of ammonia.Three:Original weight of tested Grass Carp were 10.49±0.58 g, and Grass Carp basal feed added with 0 and 7.5g/kg AKG everyday, respectively. Every cage was fed with 40 Grass Carp, every treatment group was setted 4 replicates, and the test lasted 60 days. After breeding test ending, Grass Carps with adjacent weight in control group and AKG group were selected to acute ammonia nitrogen stress for 24h. The results indicated:(1) Oxidative damage indexs:after acute ammonia nitrogen stress, lipid oxidation end-product MDA rised significantly (P<0.05) in the control group, and serum SOD, CAT, T-AOC and foregut GSH rised significantly higher in the AKG group (P<0.01), the content of MDA reduced significantly (P<0.01). It showed AKG could relieve oxidative damage resulted from ammonia nitrogen stress effectively. (2) The indexs of liver damage:After acute ammonia nitrogen stress, the activity of glutamic oxalacetic transaminas, y-glutamyl transpeptidase and adenosine deaminase in serum were significantly higher compared with control group (P<0.05), in the AKG group, the activity of glutamic oxalacetic transaminase, γ-glutamyl transpeptidase and adenosine deaminase in serum were non-significant differentiation compared with control group, the content of triglyceride and cholesterole in serum rised significantly (P<0.01), in the AKG group, the content of triglyceride and cholesterole in serum declined significantly (P<0.05) and high significantly (P<0.01). It means that adding AKG can effective alleviate liver injury caused by ammonia nitrogen stress. (3) Compared with the control group, the content of foregut lipase and midgut lipase rised highly significantly after ammonia nitrogen stress (P<0.01), the activity of midgut amylase reduced significantly (P<0.05). Compared with group Ⅱ, the content of foregut lipase and midgut lipase reduced highly significantly after ammonia nitrogen stress (P<0.01) and midgut amylase rised significantly (P<0.05) in AKG group. (4)Indexs of digestive enzyme:After acute ammonia nitrogen stress, the activity of acid phosphatase and C3 in serum rised and blood ammonia rised highly significantly (P<0.01), the activity of acid phosphatase and C3 in serum rised highly significantly (P<0.01) in AKG group, blood ammonia in serum was of non-significant differentiation. (5) The indexs of protein metabolism:After acute ammonia nitrogen stress, RNA/DNA in muscle and glutamine synthetase in serum were significantly higher (P<0.01) in AKG group, glutamic acid in serum was significantly lower than the control group (P<0.01). (6) The addition of AKG was significantly alleviated the up-regulated expression of Rhcg2 mRNA in gill、liver and Rhag mRNA in kidney、liver. In the all,these results showed that:When Grass Carp was exposed to ammonia for 24 h, the body was injured by body oxidative damage, liver damage; immunity of grass carp was declined、digestive enzyme activity was increased and so on. AKG can alleviate these phenomenon at some extent, it showed that AKG can alleviate ammonia stress effectively at some extent.