Effects Of Silymarin On Performance Of Yellow-feathered Broilers And Its Mechanism

This experiment was conducted to investigate the effects of silymarin supplementation on performance and its mechanism of yellow feather broilers.A total of 288 1-day-old rapid speed yellow-feathered broilers were randomly divided into 4 groups with 6 replicates in each group and 12 broilers in each replicate.The control group(CON)was fed with basic diet,while the low-dose group(S250 group),the medium dose group(S500 group)and the high-dose group(S750 group)were fed with 250 g / T,500 g / T and 750 g / T silymarin respectively on the basis of basic diet.The experiment lasted for 56 days,with 1 to 28 days of age in the early stage and 29 to 56 days of age in the late stage.The results are as follows:1)Compared with the CON group,silymarin supplementation markedly increased the final weight and average daily gain of broilers in the early and late stages,and decreased the feed conversion ratio(P < 0.05);There was no significant difference in the growth performance of broilers among different doses of silymarin in the early stage of the experiment(P < 0.05).The effect of medium and high dose groups on the growth performance of broilers was more significant than that of low dose group(P < 0.05).2)Relative to the CON group,diets supplementing with silymarin tended to improve the slaughter rate and eviscerated ratio of broilers(P < 0.05),and the addition of medium and high doses of silymarin could reduce the abdominal fat rate of broilers(P < 0.05).3)In comparison to the CON group,in the early stage of the experiment,silymarin supplementation can increase the content of serum TP and reduce the content of LDL-c(P <0.05),adding low and high doses of silymarin can reduce the activity of serum AST,and adding low and medium doses of silymarin can increase the content of serum HDL-c(P <0.05);In the later stage of the experiment,the addition of silymarin in the diet decreased the activity of serum ALT and the content of LDL-c(P < 0.05),and the addition of low and medium doses of silymarin decreased the content of serum TG and increased the content of HDL-c(P < 0.05).Compared with the CON group,diets supplementing silymarin increased the m RNA expression of FXR,BSEP and MRP2 in broiler liver and decreased the expression of CYP7A1 m RNA(P < 0.05).Relative to the CON group,the addition of silymarin in the diet enhanced the activities of T-AOC,SOD,CAT and GSH-Px,and increased the m RNA expression of Nrf2,GCLC and NQO1 in the liver(P < 0.05).In the early stage of the experiment,the antioxidant capacity of broiler liver increased with the increase of silymarin.In the later stage of the experiment,the effect of silymarin on the antioxidant capacity of broiler liver decreased with the increase of silymarin(P < 0.05).4)Spearman analysis of slaughter performance and liver function showed that there was a positive correlation between slaughter rate and liver CAT activity(P < 0.05);The eviscerated ratio and half eviscerated ratio were positively correlated with the expression of BSEP m RNA in broiler liver and significantly negatively correlated with the content of serum TC(P < 0.05);The abdominal fat rate was positively correlated with the expression of CYP7A1 m RNA and negatively correlated with the expression of MRP2 m RNA(P < 0.05);The rate of leg muscle was positively correlated with the expression of Nrf2 m RNA in liver and the content of AST in serum(P < 0.05).5)The expression of IL-6 m RNA in jejunal mucosa of broilers(early and later stage)supplementing with silymarin was higher than that in the CON group(P < 0.05);In addition,compared with the CON group,adding medium dose silymarin to promote the m RNA expression of IFN-γ and TNF-α in jejunal mucosa of broilers in the early stage of the experiment(P < 0.05).The addition of medium and high doses of silymarin increased the m RNA expression of Ig M(P < 0.05);In the later stage of the experiment,the addition of low and medium doses of silymarin increased the m RNA expression of Ig G in jejunal mucosa of broilers(P < 0.05),and increased the m RNA expression of IFN-γ and TNF-α in jejunal mucosa of broilers(P < 0.05).The SIg A content of jejunal mucosa in broilers supplementing with medium dose silymarin was higher than that in the CON group(P < 0.05).Compared with the CON group,medium dose silymarin supplementation increased the m RNA expression of Nrf2,GCLC and NQO1 in jejunal mucosa of broilers in the early stage of the experiment(P < 0.05),and the addition of low and medium dose silymarin increased the m RNA expression of Nrf2 and GCLC in jejunal mucosa of broilers in the later stage of the experiment(P < 0.05).6)Alpha diversity results showed that compared to the CON group,the cecal flora Chao1,Shannon,Simpson and Observed＿species of broilers in the early stage of the experiment of silymarin supplementation groups were significantly higher than that in the CON group(P <0.05).ASV / OTU Venn diagram showed that in the early stage of the experiment,the CON group and low,medium and high dose groups contained 2943,5667,4333 and 4041 unique OTU respectively;In the later stage of the experiment,the CON group and low,medium and high dose groups contained 5979,5972,5646 and 5246 unique OTUs respectively.The analysis of species composition showed that compared with the CON group,silymarin supplementation increased the relative abundance of Firmicutes(phylum level)and Faecalibacterium(genus level)in the cecum of broilers in the early stage,and decreased the relative abundance of Bacteroidetes(phylum level)and Alistipes(genus level)(P < 0.05);The addition of medium dose silymarin to the diet increased the relative abundance of Blautia in later stage of broilers,and the addition of high dose silymarin decreased the relative abundance of Tenericutes in later stage of broilers(P < 0.05).Lefse analysis showed that in the early stage of the experiment,the dominant bacteria in the CON group were Alistipes and HB2＿32＿21,AF12 and Colwellia,Faecalibacterium and Oscillospira were the dominant bacteria in the low dose group,and Lactobacillus was the dominant bacteria in the medium dose group;In the later stage of the experiment,Bifidobacterium was the dominant bacterium in the low-dose group and Anaerofustis was the dominant bacterium in the medium-dose group.7)Spearman analysis of growth performance and intestinal health showed that in the early stage of the experiment,the final weight of broilers was negatively correlated with the abundance of intestinal bacteria AF12,and positively correlated with the abundance of intestinal bacteria Lactobacillus and Oscillospira(P < 0.05);The average daily feed intake of broilers was negatively correlated with the abundance of AF12 and Alistipes(P < 0.05),and positively correlated with the abundance of Lactobacillus,faecalibacterium and the m RNA expression IFN-γ and IL-6 of jejunal mucosa(P < 0.05);The average daily gain of broilers was negatively correlated with the abundance of AF12(P < 0.05)),and positively correlated with the abundance of Lactobacillus and Oscillospira(P < 0.05);Feed conversion ratio was positively correlated with the abundance of HB2＿32＿21 and negatively correlated with the abundance of Lactobacillus and Oscillospira(P < 0.05).In the later stage of the experiment,the final weight of broilers was positively correlated with the m RNA expression of Nrf2,Ig G and IL-6 in jejunal mucosa(P < 0.05);The average daily gain of broilers was positively correlated with the abundance of Anaerofustis and the m RNA expression of Nrf2,Ig G and IL-6 in jejunal mucosa(P < 0.05);The feed conversion ratio was negatively correlated with the m RNA expression of Ig G and IL-6(P < 0.05)).In conclusion,dietary silymarin can regulate liver bile acid metabolism,improve lipid metabolism,promote slaughter performance of broilers,and enhance liver antioxidant enzyme activity and protect liver function by activating Nrf2.Dietary silymarin supplementation can improve the growth performance of broilers by increasing the abundance of beneficial bacteria in cecum,inhibiting the growth of harmful bacteria,improving the structure of cecum microflora,and enhancing the antioxidant capacity and immune function of jejunum mucosa.