Effect And Mechanism Of Ageing Corn On Production Performance And Egg Quality Of Laying Hens

Three experiments were conducted to evaluate the effects of ageing corn on lipid metabolism,antioxidant status and egg antioxidant capacity of laying hens.Experiment 1.Effect of ageing corn and soybean oil on production performance egg quality of laying hens.Four treatments were used under a 2 × 2 factorial arrangement with two types of corn(ageing corn:126mg KOH/100g or regular corn:64mg KOH/100g),and supplementation with or without soybean oil(0%or 2%)in the diets.Lohmann commercial laying hens were fed the trial diets as corn-soybean meal-based diets for 8 weeks from 51 to 58 weeks of age.Production performance were not affected by dietary treatment.Dietary ageing corn significantly decreased the serum total cholesterol,liver GSH-Px,T-SOD,ovary GSH-Px,the expression of liver GSTA3 and ovary GSH-Px of laying hens(P<0.05),and the yolk colour,yolk index at week 8,yolk reducing power,albumen DPPH value,yolk ?-tocopherol,valine,isoleucine,tryptophan,lysine,total polysaturated fatty acids,n-6 polysaturated fatty acids,yolk and albumen aroma and flavor of eggs(P<0.05);and increased the expression of liver Nrf2,SOD2,GCLC,ovary GSTA3,GSTO1,GSTT of laying hens(P<0.05);and the yolk and albumen protein carbonyl,albumen malondialdehyde and yolk monounsaturated fatty acid of eggs(P<0.05).Soybean oil supplementation significantly decreased the average daily feed intake and serum very-low-density lipoprotein cholesterol of laying hens(P<0.05),and the the valine,isoleucine,leucine,lysine,monounsaturated fatty acid,n-3 polysaturated fatty acids and n-6 polysaturated fatty acids of egg yolks(P<0.05).Soybean oil increased the methionine,valine,isoleucine,phenylalanine,leucine content of yolks.The combination of ageing corn and soybean oil would aggravate the adverse effecs of laying hens.In conclusion,ageing corn could decrease the lipoprotein content and antioxidant status of laying hens,and pale-coloured egg yolk,and induced the reduction of antioxidant capacity and nutritional value of eggs.Expriment 2.Effect of tea polyphenol on production performance and egg quality of laying hens fed diets with different levels of ageing cornA total of 288 Lohmann commercial laying hens(63-week-old)were used under a 2 ×4 factorial arrangement with four levels of dietary ageing corn(0,25%,50%,or 100%),and two levels of TPP(0 and 600 mg/kg)for 8 week.Dietary ageing corn linearly decreased the egg production(5-8 week),liver total triglyceride content and ACC expression,serum total antioxidant capacity and liver glutathione peroxidase(GSH-Px)of laying hens,and yolk index,yolk colour,albumen height and haugh unit,albumen and yolk DPPH,yolk reducing power,yolk threonine content,and linearly trend to decreased yolk n-6 polysaturated fatty acids(P=0.081),n-3 polysaturated fatty acids(P=0.087)and total polysaturated fatty acids content(P=0.077),and it linearly increased(P<0.05)the feed conversion rate(5-8 week and the whole period)and ovary malondialdehyde content of laying hens,and protein carbonyl and malondialdehyde content of eggs.Tea polyphenol supplementation increased the serum T-AOC,serum superoxide dismutase(SOD),liver SOD,liver GSH-Px,ovary SOD,GSH-Px and the expression of antioxidant-related genes of laying hens,and yolk index(at 2 week),albumen height(at 8 week),Haugh unit(at 8 week),albumen and yolk DPPH value and majority free amino acids of eggs(P<0.05),and it decreased the serum MDA content of laying hens,and albumen and yolk MDA and protein carbonyl of eggs(P<0.05).In conclusion,the ageing corn significantly linearly reduced the performance,egg quality,antioxidant status and egg antioxidant capacity of laying hens,and tea polyphenol supplementation can partially counteract the adverse effects,especially antioxidant status and egg antioxidant capacity of laying hens.Experiment 3.Effects of oxidized oils and oxidized proteins on production performance and egg quality of laying hens.A sample of 360 38-week-old Lohmann commercial laying hens was used in a 2 × 2 factorial design for 8 weeks.Dietary treatments included dietary oil(fresh corn oil or oxidized corn oil)and corn gluten meal(fresh corn gluten mea or oxidized corn gluten meal).Both dietary oxidized oil and oxidized protein decreased egg production and the average daily feed intake of laying hens.Dietary oxidized oil decreased the liver HDL-C,VLDL-C,serum total antioxidant capacity and SOD,ovary GCLC and GSH-Px expression of laying hens(P<0.05),and decreased the yolk colour(at 2,4,8 week),yolk colour(at 2 week),yolk and albumen DPPH value,reducing power,yolk a-tocopherol,xanthophyll and majority of the free amino acids and unsaturated fatty acids of eggs(P<0.05),and increased yolk and albumen malondialdehyde,yolk protein carbonyl and monounsaturated fatty acid of eggs(P<0.05).Oxidized protein decreased the liver total cholesterol,HDL-C,liver and ovary GSH-Px of laying hens,and yolk colour(at 1,2,4 and 8 week),yolk and albumen reducing power,mojarity of the free amino acids and polyunsaturated fatty acids(P<0.05),and increased the albumen and yolk malondialdehyde,albumen protein carbonyl content of eggs(P<0.05).Moreover,Flow cytometry,TUNEL,and real-time PCR revealed that both dietary oxidized oil and oxidized protein induced granulosa cell apoptosis in prehierarchical and hierarchical follicles.Furthermore,dietary oxidized oil and oxidized protein caused oxidative stress in prehierarchical and hierarchical follicles,as indicated by the downregulation of antioxidant-related-gene expression.Moreover,Wnt,FoxO1,ERK/JNK and MAPK are involved in potential apoptosis-regulation pathways,and LPAR3,FN1,INHBA,KANK1,MKP-8 and DUSP26 are involved in potential apoptosis-regulation genes in the granulosa cells of laying hens fed oxidized oil and oxidized protein.These results indicate that oxidized oil and oxidized protein decreased the production performance,lipoprotein content and antioxidant status of laying hens,and induce granulosa cell apoptosis and the reduction of antioxidant capacity of eggs via oxidative stress,and the combined use of oxidized oil and oxidized protein aggravates the adverse effects of oxidative stress in laying hens.ConclusionAgeing corn linearly reduced the performance and egg quality of laying hens.No interaction ws observed between ageing corn and soybean oil.Tea polyphenol supplementation can counteract the antioxidant status and egg antioxidant capacity of laying hens.Oxidized corn oil and oxidized corn gluten meal are the main component cause the adverse effects in ageing corn.