Effects Of Extract Powder From Puffer Fish Ovaries On Growth,Physiological Biochemistry And Tetrodotoxin Enrichment In Genetically Improved Farmed Tilapia

According to the statistics of the United Nations Food and Agriculture Organization(FAO),there are 85 countries and regions are breeding tilapia in the world.China is the largest country of breeding and exporting tilapia.The main problem which restricted the development of tilapia breeding was the outbreak of diseases under Streptococcus iniae infection in summer.The genetic improvement of farmed tilapia(GIFT)was the main breed aquaculture of tilapia in china.Traditional drug treatment and feed additives cannot solve the problem of Streptococcosis and healthy breeding of tilapia.Therefore,it is of great significance to study a new animal-derived feed additive for healthy breeding and disease control of GIFT and to prevent disease under Streptococcus iniae infection.We analyzed the blood physiological and biochemical indexes of fish,growth performance,immune response and the changes of antioxidant enzymes in liver and muscle and digestive enzymes activities in intestine of GIFT.At the same time,the effects of different levels of extract powder from puffer fish ovaries on the growth performance,blood biochemistry,immune response and tissue enrichment of tetrodotoxin and structural changes of liver and gonad were studied.This study will provide theoretical basis of a new animal-derived additive for GIFT.1.Effects of extract powder from puffer fish ovaries on growth performance,blood biochemistry and resistance to Streptococcus disease of GIFT525 GIFT with an average body weight of(0.66±0.01)g were cultured for 8 weeks and randomly divided into 7 groups,3 replicates in each group,and 25 fish per replicate,corresponding to 7 extract powder from puffer fish ovaries levels:0,0.2%,0.4%,0.8%,1.6%,3.2%,6.4%,respectively.The results showed as follows:(1)With the increasing of extract powder from puffer fish ovaries level,the body weight gain,final body weight,specific growth rate,hepatopancreas somatic index and visceral somatic index increased first,then decreased,and finally stabilized,while the value of feed conversion rate decreased significantly(P<0.05).There was no significant difference in HSI among groups(P>0.05)and the VSI of tilapia in the group of 0.8%extract powder from puffer fish ovaries was significantly higher than that in other groups(P<0.05).(2)With the increasing of extract powder from puffer fish ovaries level,the number of red blood cells,hematocrit and hemoglobin in the blood of tilapia decreased significantly(P<0.05)and the number of white blood cells increased gradually;the content of total cholesterol and the glucose in serum of tilapia decreased significantly(P<0.05),and lysozyme content in serum decreased gradually.(3)After infection,no death occurred within 24 hours in all groups of tilapias;After 48-96 hours of infection,the cumulative survival rate of tilapia in the control group was the lowest.After 192 hours of infection,the cumulative survival rate of tilapia in the group of 6.4%extract powder from puffer fish ovaries was significantly higher than that in the control group(P<0.05).Studies had shown that extract powder from puffer fish ovaries had an effect on growth performance,blood biochemistry and improved the ability of anti-Streptococcus infection of the GIFT.2.Effects of extract powder from puffer fish ovaries on antioxidant index of Liver and muscle and enzyme activity of intestinal digestive enzyme in GIFTThe changes of intestinal digestive enzymes and antioxidant enzymes in liver and muscle of GIFT fed with different levels of powder from puffer fish ovaries were studied.The results showed that cortisol,LZM and MDA in liver and muscle of Tilapia increased significantly(P<0.05),but SOD content decreased significantly(P<0.05).The activity of Na+-k+-ATPase first increased and then decreased.These differences revealed the increase of oxidative metabolism in liver and muscle and the change of digestive enzyme activity in intestine under different levels of extract powder from puffer fish ovaries.3.Effects of extract powder from puffer fish ovaries on enrichment of tetrodotoxin in GIFTThe enrichment of tetrodotoxin in liver,intestine,gonad and other tissues of tilapia at different levels of extract powder from puffer fish ovaries was determined,and the structural changes of liver and gonad tissues of tilapia were observed.The results showed that the concentration of tetrodotoxin in the liver,intestinal gonad and other 10 tissues did not exceed the detection limit of 2 ug/Kg when the level of tetrodotoxin treatment was less than 1.6%.When the level of tetrodotoxin treatment reached to 1.6%,the concentration of tetrodotoxin could be detected in the gonad of tilapia,which in intestine and gonad was much higher than that in liver.The concentration of tetrodotoxin in liver tissues of GIFT could be detected in the group of 3.2%and 6.4%extract powder from puffer fish ovaries,and the concentration of tetrodotoxin in intestine and gonad was much higher than the detection limit.We speculate that the addition of high-level extract powder from puffer fish ovaries diet will affect the normal development of liver and gonad in GIFT.