Study On Effects Of Dietary Aging Corn On Production Performance,Antioxidant Function And Intestinal Health Of Laying Hens

Corn is one of the main reserved grain varieties in China.In recent years,with the continuous increase in stock of corn in China,part of corn has been stored for more than 3 years,which is called aging corn.A portion of the aging corn is used in livestock and poultry feed after rotation.Studies have found that with the increasing storage time,the nutrient contents of corn change greatly,and the nutritional value decreases,which affect the production performance of animals.At present,there are few reports on the effects of aging corn on laying hens.Therefore,this study selected aging corn stored for 4 years to replace equivalent amount of normal corn at various levels used in the basal diet to investigate the effects of aging corn on production performance,antioxidant function and intestinal health of laying hens.This study includes the following three experiments:Trial 1 aimed to investigate the quality changes of aging corn and its effects on laying performance,serum biochemical indexs,digestive function and egg quality of laying hens.A total of 288 Hy-Line brown laying hens(60-week of age)were randomly divided into 4 groups with 6 replicates of 12 hens each.Aging corn replaced equivalent amount of normal corn at various levels used in the basal diet,and the four dietary treatments were as follows:(1)Control group: basal diet(normal corn);(2)25% aging corn group: aging corn replaced 25% amount of normal corn in the basal diet;(3)50% aging corn group: aging corn replaced half of normal corn in the basal diet;(4)100% aging corn group: aging corn totally replaced normal corn in the basal diet.The experiment period was 8 weeks after 1-week period of pretest.The results showed that compared with the control group,100% aging corn group significantly decreased the laying rate(P < 0.05);significantly reduced the contents of serum glucose(GLU)and albumin(ALB)in laying hens(P < 0.05).Hens in 50% and100% aging corn groups exhibited a significantly lower trypsin activity in anterior intestinal chyme(P < 0.05).Compared with the control group,the yolk color of egg in 100% aging corn group was significantly reduced on the 56 th day of this experiment(P < 0.05).As the replacement level of aging corn increased,the laying rate,the contents of serum GLU and ALB,the activity of trypsin in anterior intestinal chyme,and the color of egg yolk on the 28 th and 56 th day decreased linearly(Linear,P < 0.05),and the feed to egg ratio increased linearly(Linear,P < 0.05).Test 2 aimed to investigate the effect of aging corn on antioxidant function in laying hens.The experiment design was the same as that of trial 1.The results showed that compared with the control group,hens in 25% aging corn group exhibited significantly lower glutathione peroxidase(GSH-Px)and catalase(CAT)activities in serum(P < 0.05);hens in 50% aging corn group exhibited significantly lower GSH-Px activities in serum and liver,and lower ileal mucosal CAT activity,and higher liver malondialdehyde(MDA)content(P < 0.05);hens in 100% aging corn group exhibited significantly lower GSH-Px activities in serum and liver,and lower jejunal mucosal total antioxidant capacity(T-AOC),and lower ileal mucosal CAT activity(P < 0.05).100% aging corn replacement significantly decreased the superoxide anion radical scavenging capacity of serum,and the hydroxyl radical scavenging capacity of liver and jejunal mucosa(P < 0.05),and significantly increased the serum MDA content,as well as the MDA and protein carbonyl(PC)contents in liver and jejunal mucosa of laying hens(P < 0.05).Compared with the control group,hens in 50% aging corn group exhibited significantly decreased m RNA expression levels of liver superoxide dismutase 1(SOD1),jejunal mucosal CAT,and the heme oxygenase 1(HO-1)and CAT in ileal mucosa(P<0.05);hens in 100% aging corn group exhibited significantly decreased m RNA expression levels of GPX1 and CAT in liver,and SOD1,SOD2 and CAT in jejunal mucosa,as well as HO-1 and CAT in ileal mucosa(P<0.05).As the replacement level of aging corn increased,the activity of serum GSH-Px,T-AOC and activities of GSH-Px and CAT in liver,the T-AOC and CAT activity of jejunal mucosa,the ileal mucosal CAT activity,serum superoxide anion scavenging capacity,and hydroxyl free radical scavenging capacities of liver and jejunal mucosa,the m RNA expression levels of liver GPX1,the m RNA expression levels of HO-1,NAD(P)H: quinone oxidoreductase 1(NQO1),GPX1,SOD1,SOD2 and CAT in jejunal mucosa,and the m RNA expression levels of HO-1 and CAT in ileal mucosa showed linear decreases(Linear,P < 0.05).The m RNA expression levels of liver nuclear factor erythriod 2-related factor 2(Nrf2)and ileal mucosal NQO1 showed quadratic decreases(Quadratic,P < 0.05).The activity of ileal mucosl CAT and m RNA expression levels of SOD1 and CAT in liver showed linear and quadratic decreases(Linear,P < 0.05;Quadratic,P < 0.05).The MDA contents of serum and jejunal mucosa,and PC contents of liver and jejunal mucosa were increased linearly(Linear,P < 0.05),and the liver MDA content showed linear and quadratic increases(Linear,P < 0.05;Quadratic,P < 0.05).Test 3 aimed to investigate the effects of aging corn on intestinal immune function,apoptosis and intestinal barrier function of laying hens.The experiment design was the same as that of trial 1.The results showed that compared with the control group,hens in 50% aging corn group exhibited significantly decreased zonula occludens protein 1(ZO-1)m RNA expression levels in jejunal mucosa and increased tumor necrosis factor-α(TNF-α)content in ileal mucosa(P < 0.05);hens in 100%aging corn group exhibited significantly decreased immunoglobulin G(Ig G)content,and m RNA expression levels of claudin 2(CLDN2)and ZO-1 in jejunal mucosa(P <0.05),and significantly increased serum diamine oxidase(DAO)activity,increased jejunal mucosal interferon-γ(IFN-γ)content and ileal mucosal TNF-α content(P <0.05).As the replacement level of aging corn increased,the jejunal mucosal Ig G content,the m RNA expression levles of CLDN2 and ZO-1 in jejunal mucosa showed linear decreases(Linear,P < 0.05);the serum DAO activity,jejunal mucosal IFN-γcontent,and TNF-α m RNA expression levels of jejunal mucosa,and ileal mucosal TNF-α content showed linear increases(Linear,P < 0.05);and the content of jejunal mucosa TNF-α showed a quadratic increase(Quadratic,P < 0.05).In summary,it can be concluded as follows:1.Lipid peroxidation and protein oxidation have occurred in aging corn.Various replacement levels of aging corn decrease the laying rate of hens,and 100% aging corn replacement significantly decreases laying rate,and results in a reduction of yolk color.This is related to the decrease of the digestibility of nutrients,antioxidant function and intestinal health of laying hens.2.Various replacement levels of aging corn decreases the antioxidant capacity of laying hens,causes accumulation of lipid and protein oxidation products in serum and tissues,and induces oxidative damage to hens.The 100% aging corn replacement shows the most serious effect on laying hens.3.Aging corn replacement level at more than 50% decreases the intestinal immunity,induces intestinal inflammation,and impairs intestinal barrier function of laying hens.