Effects Of Dietary Energy Levels And Lipopolysaccharide Challenge On Growth Performance,Energy Metabolism And Liver Health In Meat Duck

A study was conducted to determine the alleviation of dietary energy levels on lipopolysaccharide(LPS)challenge in meat duck aged from hatching to 21 days based on growth performance,serum biochemical parameters,intestinal development,jejunal morphology,hepatic lipid metabolism,and hepatic inflammation.The study included ? and ? phases.Phase I was from hatching to 14 days of age.During phase ?,five experimental diets contained 3200,3100,3000,2900 and 2800 kcal/kg of metabolizable energy(ME).Each dietary treatment consisted of twelve replicate cages of 10 birds.Then on d 15,all birds went into Phase II(from 15 to 21 days of age).During phase II,12 replicate cages in each dietary treatment were divided into two groups,ducks in one group(6 replicate cages)were given LPS(500 ?g/kg BW)by intraperitoncal injection at 15,17,19 days of age;And ducks in the other groups were given the equal volume saline at the same time.The results showed:1)During phase I,ducks fed 2800 kcal/kg ME of diet significant increased(P<0.05)body wcight(BW),body weight gain(BWG)when compared with ducks fed other diets.With the increase of dietary energy level,F:G linearly decreased(P<0.05),and ducks fed 3200 kcal/kg ME of diet had the lowest F:G and ADFI(P<0.05)than ducks fed other diets.Diets containing 2800,3100 and 3200 kcal/kg ME had hfigher(P<0.05)total retention energy(TRE)compared to diets containing 2900 and 3000 kcal/kg ME.Under LPS injection,ducks lowered(P<0.05)BW,BWG,ADFI,TRE and total energy intake when compared with ducks under saline injection.There were on interactive effects on growth performance between dietary energy levels and LPS injection.2)Dietary energy levels had a significant effect(P<0.05)on serum alkaline phosphatase(AKP)activities and glucose(GLU)content at 21 d of age.Ducks fed diet with 2900kcal/kg ME had higher(P<0.05)serum AKP activities than fed diets with 3100 and 3200 kcal/kg ME.And diet with 2800kcal/kg ME had lower(P<0.05)serum GLU content than diets with other energy levels.LPS injection significantly increased(P<0.05)serum total protein(TP)and high-density lipoprotein cholesterol(HDL),and decreased(P<0.05)serum glutamic oxalacetic transaminase(AST).There was a significant interactive effect(P<0.05)on serum TP,GLU and HDL between dietary energy levels and LPS injection.3)Dietary energy levels had a markedly effect on(P<0.05)liver weight(14 d).Ducks fed diet with 2800kcal/kg ME had higher liver weight(14 d)than fed other dietary treatments,LPS treatments significantly decreased(P<0.05)the weight of heart,lung and kidney,and increased(P<0.05)the percentage of gizzard and proventricular.4)LPS injection significantly increased(P<0.05)the relative length of intestine,and decreased(P<0.05)the pH of digesta in gizzard.There was a significant interactive effect(P<0.05)on the relative length of duodenum,jejunum and cecum,and jejunal villus height and mucous layer thickness between dietary energy levels and LPS injection.5)LPS injection decreased(P<0.05)the liver weight and the content of lipid in liver,but increased the mRNA expression of fatty acid synthase(FAS)and acetyl-CoA carboxylase(ACC)in liver.There was a significant interactive effect(P<0.05)on the mRNA expression of ACC between dietary energy levels and LPS injection.6)The mRNA expression of hepatic IL-6 in diets with 3200 and 3100kcal/kg ME was higher(P<0.05)than diets with 2800,2900 and 3000kcal/kg ME.And the mRNA expressions of hepatic IFN-y and TGF-P in diets with 3100kcal/kg were also higher than diets containing 2800 and 2900 kcal/kg ME.LPS injection significantly increased(P<0.05)the mRNA expressions of hepatic IL-6,IL-10,TGF-? and AVBD-10.There was a significant interactive effect(P<0.05)on the mRNA expression of hepatic IL-6?IFN-??TGF-??AVBD-10 and INOS between dietary energy levels and LPS injection.These results suggested that ducks(1-14 d)fed diet with 2800 kcal/kg ME presented the best growth rate.LPS injection decreased the growth performance,destroyed intestinal morphology,changed the lipid metabolism in liver,and caused the inflammation of liver in meat ducks.Under LPS stress conditions,ducks which fed diet with 3200 had a significant impact on jejunum morphology,lipid metabolism and inflammatory factor expression in meat ducks.