| Mercury widely exists in the environment,and is considered to be one of the main environmental pollutants because of its high toxicity and high mobility in the ecosystem.The toxic effect of mercury on livestock and poultry body by polluting water source and feed and then accumulating in livestock and poultry body.However,the effects of mercury on the performance of broilers,the residual regularity,and the toxic mechanism of mercury on the main target organs of broilers are not systematically studied,and the studies on antagonizing the harm of mercury to livestock and poultry by plant-derived antioxidants are few.Therefore,the purpose of this study is to reveal the effects of different doses of mercury in diet on the growth performance of broilers,the distribution of mercury in the tissues of broilers,and the toxic effects of mercury on liver and kidney,and to explore the effect of GSPE on alleviating the toxicity of mercury to broilers.240 1-day-old rose 308 broilers were randomly divided into 6 treatment groups: 0 mg/kg,5 mg/kg,10 mg/kg,25 mg/kg,50mg/kg Hg and 50 mg/kg Hg + 450 mg/kg GSPE.Each group had 5 replicates,8chickens per replicate,and the test period was 6 weeks.During the experiment,the food intake and body weight gain were recorded,and the feed to meat ratio was calculated.The blood,liver,kidney,feather,breast muscle and other tissue samples were collected at the 3rd and 6th weekend respectively.The residual mercury in tissues,serum biochemical indexes,pathological examination of liver and kidney,antioxidant capacity of liver and kidney and expression of related genes were measured.The main results are as follows:1.The effect of dietary Hg and the alleviative effect of GSPE on growth performance of BroilersIn the 3rd week,compared with the control group,50 mg/kg Hg significantly reduced the ADFI、ADG(P < 0.05),and significantly increased the feed to meat ratio(P < 0.05).GSPE significantly increased the ADFI 、 ADG(P < 0.05),and significantly reduced the feed to meat ratio(P < 0.05).In the 6th week,50 mg/kg Hgsignificantly reduced the ADFI of broilers(P < 0.05),while GSPE significantly increased the daily intake of broilers(P < 0.05).2.The effect of dietary Hg and the alleviative effect of GSPE on Hg residue in broilersIn the 3rd week,10,25 and 50 mg/kg Hg significantly increased the mercury content in breast,liver,kidney and feather(P < 0.05),and GSPE significantly reduced the mercury content in breast,kidney and feather(P < 0.05).In the 6th week,25 and50 mg/kg Hg significantly reduced the mercury content in breast muscle,10,25 and50 mg/kg Hg significantly reduced the mercury content in kidney(P < 0.05),and the mercury content in liver and feather increased significantly with the increase of Hg content in diet(P < 0.05).The addition of GSPE had no significant effect on mercury content in broiler tissues(P > 0.05).In the 3rd and 6th week,the content of mercury in breast muscle,liver,kidney and feather showed a strong linear correlation with the addition of mercury in diet.In the same treatment group,mercury residue was the highest in feather,followed by kidney and liver,and the lowest in pectoral muscle.When the mercury content in the daily food is higher than 10 mg/kg,the mercury content in breast muscle is higher than the standard limit value of total mercury(0.05 mg/kg)in meat in GB 2762-2017.3.The effect of dietary Hg and the alleviative effect of GSPE on liver injury of broilersDietary mercury exposure caused damage to the liver of broiler.Liver pathology showed that all the doses of mercury caused damage to the liver structure of broilers in the 3rd and 6th weeks,which showed that fatty degeneration of liver cells,round vacuoles in the cytoplasm,infiltration of inflammatory cells in the portal area,and necrosis of a small number of cells in the inflammatory focus.Serum biochemical indicators showed that 10 mg/kg、25 mg/kg and 50 mg/kg Hg significantly increased serum ALT activity(P < 0.05),50 mg/kg Hg significantly increased serum AST and ALP activity(P < 0.05)at week 3;25 mg/kg and 50 mg/kg Hg significantly increasedserum ALT and AST activities(P < 0.05),50 mg/kg Hg significantly decreased serum TP content(P < 0.05)at week 6.Liver antioxidant indicators showed that 10 mg/kg and 25 mg/kg Hg significantly reduced the activity of CAT in liver(P < 0.05),while50 mg/kg Hg significantly reduced the activity of SOD,CAT(17.7%)and GPX in liver(P < 0.05),the level of MDA in liver was significantly increased(P < 0.05)at week 3;5 mg/kg Hg significantly reduced the activity of GPX in liver(P < 0.05),10mg/kg、25 mg/kg and 50 mg/kg Hg significantly reduced the SOD and GPX in liver(P < 0.05),and significantly increased the MDA content in liver(P < 0.05)at week 6.In addition,50 mg/kg Hg significantly inhibited the m RNA expression of Nrf2,NQO1 and gpx1 in the liver(P < 0.05),and promoted the m RNA expression of Keap1(P <0.05).Adding 450 mg/kg GSPE to the diet alleviated Hg-induced liver pathological changes,significantly reduced the activities of AST and ALT in serum(P < 0.05),significantly increased the activity of liver SOD and reduced the level of MDA(P <0.05).At the same time,compared with the Hg group,GSPE promoted liver Nrf2 and gpx1 m RNA expression and inhibited the m RNA expression of Keap1(P < 0.05).4.The effect of dietary Hg and the alleviative effect of GSPE on kidney injury of broilersDietary mercury exposure caused damage to the kidney of broiler.Renal pathology showed that all the doses of mercury caused damage to the kidney structure of broilers in the 3rd and 6th weeks,the tubular degeneration,unclear tubular structure,inflammatory cell infiltration,fibrosis and necrosis of a small number of cells were seen.Serum biochemical indicators showed that 50 mg/kg Hg significantly increased(P < 0.05)the serum BUN,crea and TG contents,and decreased the serum CHOL content(P < 0.05)at week 3;25 mg/kg Hg significantly increased CREA(P <0.05),50 mg/kg Hg significantly increased the contents of BUN,CREA and TG in serum(P < 0.05)at week 6.Kidney antioxidant indicators showed that 5 mg/kg、10mg/kg、25 mg/kg Hg significantly reduced the activity of GPX in kidney(P < 0.05),50 mg/kg Hg significantly decreased(P < 0.05)renal CAT and GPX activity andsignificantly increased(P < 0.05)renal MDA level at week 3;5 mg/kg and 10 mg/kg Hg significantly reduced the activity of CAT(P < 0.05),25 mg/kg and 50 mg/kg Hg significantly decreased the renal CAT and GPX activities(P < 0.05),50 mg/kg Hg significantly increased the content of MDA in kidney(P < 0.05)at week 6.In addition,50 mg/kg Hg significantly inhibited the m RNA expression of Nrf2 and gpx1 in the kidney(P < 0.05),and promoted the m RNA expression of Keap1(P < 0.05).Adding 450 mg/kg GSPE to the diet alleviated Hg-induced kidney pathological changes,significantly reduced the activities of serum BUN and CREA(P < 0.05),and significantly increased the activities of renal CAT and GPX(P < 0.05),significantly reduced the level of renal MDA(P < 0.05).At the same time,compared with the Hg group,GSPE promoted renal Nrf2、HO-1 and gpx1 m RNA expression and inhibited the m RNA expression of Keap1(P < 0.05).In conclusion,the following conclusions can be drawn:(1)adding 50 mg/kg Hg can significantly reduce the growth performance of broilers in the third week.(2)The content of Hg in breast muscle,liver,kidney and feather showed a strong linear correlation with the addition of Hg in diet.The distribution rule of Hg in broiler body was feather > kidney > liver > muscle.(3)When the concentration of mercury in the diet reaches 10 mg/kg,it can cause liver damage and oxidative stress in broilers.When the concentration of mercury in the diet reaches 25 mg/kg,it can cause kidney damage and oxidative stress in broilers.(4)Proanthocyanidins can alleviate the decrease of growth performance induced by mercury,which may improve the antioxidant capacity of liver and kidney and alleviate the damage of liver and kidney caused by mercury by activating Nrf2 signal pathway. |
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