Effects Of Mulberry Leaf Extract On Abdominal Fat Deposition In Broilers And Its Mechanism

Abdominal fat deposition in broilers is an important factor affecting its commercial traits and energy consumption.Mulberry leaf extract(MLE)has anti lipid,hypoglycemic,antibacterial and other effects,but its mechanism of action on fat metabolism is not clear,and its effect on abdominal fat deposition in broilers is rarely reported.In this study,the effects and mechanism of mulberry leaf extract on regulating abdominal fat deposition of AA broilers were investigated by measuring growth performance,blood indices,intestinal morphology and structure,microflora and genes associated with fat metabolism in the liver.A total of 1921-day-old healthy AA broilers(whole females)with similar body weight were randomly divided into 4 treatments,with 6 repetitions for each treatment and 8 chickens for each repetition.The four treatments were: control group(basal diet);400 mg/kg MLE group(basal diet +400 mg/kg Mulberry leaf extract);800 mg/kg MLE group(basal diet +800 mg/kg Mulberry leaf extract);1200 mg/kg MLE group(basal diet +1200 mg/kg Mulberry leaf extract).The pre-trial period is 3 days,and the experimental period is 3-56 days old,which is divided into two stages: 3-21 days old(early stage)and 22-56 days old(late period).Relevant samples were collected at the age of 21 and 56 days for determination.Research indicates:1)Production performance : Each level of MLE had no significant effect on the average daily feed intake(ADFI),average daily gain(ADG)and feed-to-weight ratio(F/G)of broilers throughout the period.2)Abdominal fat weight: All MLE groups significantly decreased the abdominal fat weight of broilers in the whole period(P<0.05),and with the increase of MLE supplemental level,the decrease of abdominal fat weight in the later period also increased,which was decreased by 30.38%,36.32% and 44.9% in the three levels groups,respectively.3)Lipid metabolism-related indexes in serum and liver: supplementation of 800 and1200 mg/kg MLE significantly decreased serum total cholesterol(TC)content in early and late stage,and supplementation of 1200 mg/kg MLE significantly increased serum high density lipoprotein(HDL-C)content in late stage(P<0.05);TC content in liver was significantly decreased with the increase of the dose of MLE group(P<0.05).4)Intestinal morphology: The addition of MLE delayed the development of duodenum and ileum in the early stage of broilers,but effectively improved the intestinal morphology of duodenum and jejunum in the late stage of broilers,and had no significant effect on ileum,as follows:In the early growth stage of broilers,adding 800 mg/kg and 1200 mg/kg MLE significantly increased the crypt depth of duodenum of broilers(P<0.05),and the flux-crypt ratio of ileum of broilers at all levels was significantly decreased(P<0.05).At the late growth stage of broilers,adding 800 mg/kg and 1200 mg/kg MLE significantly increased the villus height of duodenum and jejunum of broilers(P<0.05).5)Cecum microflora: Mulberry leaf extract can improve the cecum microflora structure and diversity of broilers.At phylum level,Firmicutes and Bacteroidetes were the dominant phyla in cecum.There was no significant difference in Firmicutes and Bacteroidetes among all groups.The relative abundance of Firmicutes in 800 mg/kg MLE group was slightly higher than that in control group,and bacteroidetes was slightly lower than that in control group(P>0.05).At the genus level,Bacteroides,Streptococcus,uncultured,Rikenella and Lactobacillus are the dominant genera in cecum.Analysis by Kruskal-Wallis and Metastats screened out microorganisms with differences between groups and found that,compared with the control group,Adding appropriate MLE can significantly increase Alistipes,Phascolarctobacterium,Coprococcus,Bifidobacterium and Eubacterium Hallii Group,Faecalibacterium and CHKCI001 in cecum of broilers(P<0.05),but significantly decreased the level of CHKCI002(P<0.05).6)The expression of fat metabolism-related genes in the liver: the addition of different levels of MLE increased the m RNA expression of adenylate-activated protein kinase(AMPK)in the liver of broiler chickens(P<0.05).The addition of 800 mg/kg and 1200 mg/kg of MLE significantly reduced the sterol regulatory element-binding protein-1c(SREBP-1c),acetylCo A carboxylase(ACC)and acetyl-Co A carboxylase(FAS)m RNA expression(P<0.05),but the m RNA expression of peroxisome proliferator-activated receptor α(PPARα),carnitine palmitoyltransferase 1α in broiler liver(CPT1α),acyl-Co A oxidase(ACOX),lipoprotein lipase(LPL),and liver-type fatty acid-binding protein(L-FABP)gene expression levels had no significant effect(P>0.05).In conclusion,mulberry leaf extract can reduce abdominal fat deposition and improve intestinal morphology and cecum microflora structure of AA broilers.The mechanism of mulberry leaf extract to reduce abdominal fat deposition was as follows: Mulberry leaf extract significantly increased the expression of AMPK m RNA in liver,and significantly lowered the expression of SREBP-1c,FAS,ACC m RNA in liver which is related to fat metabolism.By reducing fat synthesis,the content of TC in liver and serum was reduced,and its mechanism may be associated with AMPK/ SREBP-1c /ACC pathway.