| In this thesis, to explore and study the occurrence of fish liver disease and development of mechanisms and processes, and screen drugs or feed additives so as to provide experimental platform, we establish the grass carp liver injury model and its corresponding evaluation system throught Injecting thioacetamide (TAA) into abdominal and feeding different levels of oil. At the same time, we add respectively yeast culture, curcumin and silymarin to the feed and feed grass carp which is injuryed in the liver to explore the protective effect on the damaged liver and pancreas of the three substances and provide reference for its application in grass carp feed.Test 1 is that establishing the grass carp liver injury model throught injecting TAA into abdominal and feeding different levels of oil. Injecting TAA (300mg/kg, once per day) into abdominal and feeding respectively feed which is composed of 1.32% oil, 3.61% oil or 5.83% oil. Meanwhile, we feed the corresponding fat level as a control group but not inject TAA, a total of six experimental groups, each with 4 replicates. Average weight of grass carp were 30.0±4.0g, were randomly divided into 24 experimental cages, 20 fish per cage, in the indoor concrete ponds hanging cage, feeding for 10 weeks. The results showed:①compared with the control group, grass carp specific growth rate (SGR) of TAA group significantly decreased by 30.5% (P<0.01), but the survival rate (SR) in 68.0% or more. The fat content of whole fish of TAA group reduced by 3.53% (P>0.05), muscle fat content decreased by 17.60% (P<0.05), while the fat content in hepatopancreas increased by 13.38% (P<0.01); with the oil level increased by from 1.32% to 5.83% , fat content of liver and pancreas of model group were significantly lower (P<0.05).②TAA group at 2 weeks, 4 weeks and 6 weeks, the AST/ALT in the serum is respectively 1.94 times, 1.38 times and 1.31 times as much as control groups. 10 weeks later, AST/ALT in the serum of TAA group increased by 10.1% (P>0.05), and cholinesterase (CHE) decreased 6.38% (P>0.05). TAA serum superoxide dismutase (SOD) activity was significantly lower than control group 8.56% (P<0.05).③Compared with the control group, 4 weeks later, in the TAA group, liver cell swelling, some inflammatory infiltration, fatty degeneration of liver cells increased with the feed fat level increasing. 10 weeks later, in the TAA group, liver cell swelling and fuzzy boundaries, part of the lipid abnormalities and inflammation, and the degree of liver fibrosis also increased. with the dietary fat level increasing. The reasults showed that we establish the grass carp liver injury model which is characteristic of fatty liver and liver fibrosis.Test 2 is the protection of three additive to grass carp (Ctenopharyngodon idellus) whose livers were injured by TAA. Injured liver experimental model was set up by the following method:grass carp,were injected with TAA in abdominal cavity, 300 mg/kg,once per day, and were feed by forage including 3.61% fat. We established 5 groups and every group had 4 repetition. Group1: control group(not injecting TAA, feeding with forage including 3.61% fat; Group2: model group; Group3: model + 0.75‰yeast culture; Group4: model+1.40‰curcumin; Group5: model+0.83‰Silymarin. The reasults were that:①the SGR of group 3, 4 and 5 were higher 48.68%, 28.95% and 17.11% than group 2 responsively and lower than the group 1, but there was no significant difference(P>0.05)among the groups; there had significant differences between injection of TAA and protecting agent to the Liver index (LBR) and composition of body fat content.②At 2 weeks, 4 weeks and 6 weeks AST/ALT values of serum of experimental group significantly different (P<0.05), AST/ALT of three protective agent group were significantly lower than the model group, while significantly higher than control group (P<0.05); 10 weeks later, the AST/ALT of serum was no significant differences among three experimental groups. TAA and three additives significantly affected on the T-SOD and GSH-PX in the serum (P<0.05), yeast DV group and the curcumin group T-SOD, GSH-PX was significantly higher than the model group (P<0.05), and silymarin group and model group was not significant difference (P>0.05).③Compared with model group, 4 weeks later, liver cells of three additives group arranged in neat rows, the lesion was reduced. 10 weeks later, in the model group, cell swelled and had blurred boundaries, some diseases and inflammatory infiltration of fat, and the hepatic fibrosis emerge; liver cells of three additives groups arranged in neat rows, cell outlines clear, some fatty degeneration, while silymarin group there are some inflammatory infiltration. The reasults showed that the feed that is added respectively 0.75‰DV yeast, 1.40‰curcumin or 0.83‰silymarin has a protective effect to the damaged liver and pancreas, but were not completely restored to the physiological state of the control group of grass carp.Summary:Ten weeks later, we establish the grass carp liver injury model which is characteristic of fatty liver and liver fibrosis based on growth performance, mainly physiological, liver and pancreas morphology and histological observation results throught Injecting TAA (300mg/kg, once per day) into abdominal and feeding respectively feed which is composed of 1.32% oil, 3.61% oil or 5.83% oil. The feed that is added respectively 0.75‰DV yeast, 1.40‰curcumin or 0.83‰silymarin has a protective effect to the damaged liver and pancreas, but were not completely restored to the physiological state of the control group of grass carp. |
