A Comparative Study On Ammonia-nitrogen Tolerance,disease Resistance And Muscle Nutrition Of The Self-cross And Cross F₁ Generations Of Misgurnus Anguillicaudatus And Paramisgurnus Dabryanus

Misgurnus anguillicaudatus and Paramisgurnus dabryanus are important economic fishes in China.Relatively,the P.dabryanus grows faster and is larger,while the M.anguillicaudatus has more delicious meat,market acceptance and higher prices.With the increasing market demand,it is very important for the healthy development of loach farming to breed hybrid loach species with delicious meat,strong resistance and fast growth.In order to study the differences in ammonia nitrogen tolerance,disease resistance and muscle nutrition between the hybridization of M.anguillicaudatus and P.dabryanus,and to provide the basis for the breeding of new varieties,four species of Loach were obtained through self-crossing and cross-breeding of Loach and Paramisgurnus dableanus.The M.anguillicaudatus ♀ x M.anguillicaudatus(MM),M.anguillicaudatus ♀ x P.dabryanus(MP),P.dabryanus ♀ x M.anguillicaudatus(PM),P.dabryanus ♀ x P.dabryanus(PP),breeding to four months later,keep the water temperature in 20.0 ± 1.0℃,keep more than 5.0 mg/L.A series of related studies were carried out under the condition that pH was maintained at 7.5.The main results are as follows:1.Comparative study on ammonia-nitrogen tolerance of self-crossing and hybrid F1 generation of M.anguillicaudatus and P.dabryanus.(1)The semi-lethal concentration of ammonia nitrogen of four species of loach was detected under the experimental conditions of six gradient concentrations of NH4Cl,namely 0 mg/L(control group)、200 mg/L、400 mg/L、800 mg/L、1600 mg/L and 3200 mg/L.The order from high to low lethal concentration of total ammonia of the four loachies was:MM(1212 mg/L)>PP(984 mg/L)>MP(857 mg/L)>PM(681 mg/L),and non-ionic ammonia lethal concentration was:MM(60.39 mg/L)>PP(49.03 mg/L)>MP(42.79 mg/L)>PM(34.00 mg/L).MM showed the strongest ammonia nitrogen tolerance,and MP with Loach as the female parent was also stronger than PM with P.dactylus as the female parent,showing a strong maternal effect.(2)The activities of superoxide dismutase,lysozyme and phosphatase in the muscles and liver of four species of eachfish were detected at 0 mg/L(control group)and 200 mg/L under NH4Cl stress for 24h.The research results of superoxide dismutase are as follows:In the control group,the activity of superoxide dismutase in the muscles and liver of the four species of loachies was between 147.79±46.54 U/mL～203.98± 10.65 U/mL and 179.95±9.27 U/mL～205.00± 10.20 U/mL,respectively,showing a trend of MM>PP>MP>PM.There was no significant difference among all groups(P>0.05).In the experimental group,the activities of superoxide dismutase(SOD)in the muscles and liver of the four species of Portia were significantly increased(P<0.05),by 18.98%～21.36%and 3.58%～11.59%respectively.The results of lysozyme study are as follows:In the control group,lysozyme activity in the muscles and liver of the four species of boach was between 7.25±2.69 U/L～7.81 ±0.74 U/L and 7.96±0.47 U/L～8.57±0.38 U/L,respectively,showing a trend of MM>PP>MP>PM with no significant difference between each group(P>0.05).In the experimental group,lysozyme activity of the four species of botia superciliaris was significantly increased(P<0.05),the increase rates were 17.34%～26.90%and 10.84%～23.80%.The results of phosphatase study are as follows:In the control group,the activity of phosphatase in the muscles and liver of the four species of loachies was between 31.25±4.43 IU/L～40.80± 1.73 IU/L and 37.46±3.22 IU/L40.32±3.56 IU/L,showing a trend of MP>PP>MM>PM.There was no significant difference between each group(P>0.05).In the experimental group,the phosphatase activity of the four species of botia superciliaris was significantly increased(P<0.05),and the increase rates were 11.42%～28.92%and 8.09%～21.03%.Under ammonia-nitrogen stress,the activities of superoxide dismutase,lysozyme and phosphatase in muscle and liver of fish and their increasing rates reflected the ammonia-nitrogen tolerance of the four species of loaches to some extent.The four species of loach all have good self-regulation and can improve the ability of ammonia nitrogen tolerance by increasing the activities of superoxide dismutase,lysozyme and phosphatase.The ammonia nitrogen tolerance of MM and PP in self-crossing group was better than that of MP and PM in crosscrossing group.The increase rate of phosphatase activity and lysozyme activity in MP group was better than that in PM group.The combination with loach as female parent had better performance in ammonia nitrogen tolerance,and the ammonia nitrogen tolerance was stronger.In terms of the rate of enzyme activity increase,the progeny with P.dabryanus as mother parent had better performance.M.anguillicaudatus as female parent offspring after stimulation,several kinds of enzymes speed is higher than the sensitivity of the loach as female parent,the higher enzyme activity increase rate that is sensitive to the ammonia nitrogen stress,the lower the tolerance,illustrates several level of the ability of resistance to ammonia nitrogen in close connection with the can by enzyme activity changes in response to its level of the ability of resistance to ammonia nitrogen.2.Comparative Study on resistance to Aeromonas veronii of self-crossing and hybrid F1 generation of M.anguillicaudatus and P.dabryanus.(1)The isolation,purification and identification of to resist A.veronii from the body of the sick gold loach were conducted.(2)The semi-lethal concentrations of autocross and hybrid offspring of loach and paraplegia clinensis were determined under the concentration of 1×106、1×107、1×108、1×109、1×1010 CFU/mL.The results showed that the order of the semi-lethal dose of the four species of aeromonas auricularis was MM(3.55×107 CFU/mL)≈PP(3.55×107 CFU/mL)>MP(1.26×107 CFU/mL)>PM(7.94×106 CFU/mL).The resistance of MM and PP in the self-crossing group was stronger than that of MP and PM in the cross group,and the resistance of MM and MP in the female parent of Loach was stronger than that of PP and PM in the female parent of P.davidianus.(3)The activities of superoxide dismutase,lysozyme and phosphatase in the muscles and liver of the four species of Portia superoxide were detected 24h after infection with aeromycete at 0 CFU/mL and 1×106 CFU/mL(control group)of A.veronii.In the control group,lysozyme activity in muscle and liver of the four species of porpoise was between 8.20±0.58 U/L～8.55±0.35 U/L and 8.33± 1.02 U/L～9.03±0.69 U/L.In the experimental group,lysozyme activity of the four species of botia superciliaris was significantly increased(P<0.05),and the increase rate was 15.79%～25.45%.The research results of superoxide dismutase are as follows:In the control group,the activity of superoxide dismutase in the muscles and liver of the four species of porpoise was between 175.66±8.11 U/mL and 197.97±9.63 U/mL and 178.12±9.96 U/mL and 203.09±9.73 U/mL,respectively,showing a trend of MM>PP>MP>PM.There was no significant difference between the two groups(P>0.05).In the experimental group,SOD activity of the four species of loach was significantly increased(P<0.05),with the increase rate ranging from 8.19%to 12.99%.In the control group,the activity of phosphatase in the muscles and liver of the four species of porcine adult fish was between 35.46±2.98 IU/L～40.08±3.22 IU/L and 35.75±3.16 IU/L～39.41 ±3.00 IU/L,showing a trend of MP>MM>PP>PM,but there was no significant difference between each group(P>0.05).In the experimental group,the activity of phosphatase in the muscles of the four species of botia superciliaris was significantly increased(P<0.05),and the increase rate was 14.16%～23.0%.The activities of superoxide dismutase(SOD),lysozyme and phosphatase(LP)in muscle and liver of fish infected with A.veronii reflected the anti-A.veronii ability of the four species of loaches to some extent.All the four species of loaches could improve their resistance to A.veronii by improving the activities of superoxide dismutase,lysozyme and phosphatase through self-regulation.The resistance of MM and PP in self-crossing group to A.veronii was better than that of MP and PM in cross group.The half lethal amount of A.veronii,the increase rate of phosphatase activity and lysozyme activity in MP group were higher than those in PM group.The combination with loach as female parent showed better resistance to A.veronii.Large scale vice loach as female parent offspring after stimulation,several kinds of enzymes speed is higher than the sensitivity of the loach as female parent and higher enzyme activity increase rate shows that the vickers single spore fungus infection is more sensitive to gas,the lower the tolerance,illustrates several resistance ability of bacterium in close connection with the can by enzyme activity changes in response to its level of the ability of resistance to ammonia nitrogen.3.A comparative study on the muscle nutrients of self-crossing and hybrid F1 generation of M.anguillicaudatus and P.dabryanus.The indexes of muscle nutrients,amino acids,fatty acids and other indexes of self-crossing and F1 hybrid of four seeds were analyzed.The results showed that MP(19.22±0.56)%≈MM(19.22±0.72)%>PP(17.41 ±1.25)%>PM(14.81.±2.21)%was the order of the contents of crude protein in the four seeds from high to low.The proportion of essential amino acids in total amino acids from high to low is:MM(41.25%)>MP(40.76%)>PM(40.73%)>PP(40.68%);The proportion of the total amino acids of umami flavor in the total amino acids from high to low was:MM(38.98%)>MP(38.86%)≈PP(38.86%)>PM(38.57%).The order of the crude fat content of the four self-crossing and hybrid offspring was PM(8.11±2.43)>MP(6.50±2.12)>pp(3.62±1.12)>MM(1.02±1.54).Among the amino acid scores of the four species of loach,threonine,isoleucine,leucine and lysine were all higher than 1.The composition of fatty acids in muscle was changed by hybridization,37 kinds of fatty acids were detected in MM,35 kinds of fatty acids were detected in MP and PM,and 33 kinds of fatty acids in PP.The contents of monounsaturated fatty acid(MUFA),C18:3N6(-methyl linolenic acid)and C18:1N9C(methyl oleate)in the hybrid PM and MP were significantly higher than those in the self-crossbred.The four species of loach are rich in nutrition and are good source of protein.MP was better than MM,PP and PM in crude protein content,and PM was better than MM,PP and MP in crude fat content.The musculature umami of MM and MP with Loach as female parent was better than PP and PM with P.dabryanus as female parent.The muscle of MP and PM of cross progeny were rich in mono unsaturated fatty acids and were better protein sources.In conclusion,the self-crossing progenies of Mm and PP are stronger than the crossbred progenies MP and PM in terms of ammonia nitrogen resistance and A.veronii resistance.The progeny with loach as female parent was stronger in ammonia nitrogen tolerance and A.veronii resistance than the progeny with P.dabryanus as female parent.The PP and PM of the progeny with P.dabryanus as the mother parent were more sensitive to the environmental changes,and the enzyme activity in the progeny increased faster than that of the progeny with P.dabryanus as the mother parent.The content of crude fat in MP and PM of crossbred progeny was better than that in MM and PP of self-bred progeny.In terms of umami amino acid content,the progeny with Loach as female parent was better than the progeny with P.dabryanus as female parent.