Production Of Eggs Enriched With N-3 PUFA By Dietary Nannochloropsis Sp.and Its Mechanism In Laying Hens

Three studies had been accomplished to evaluated nutritional values of Nannochloropsis sp.(NS),its effects in diet of laying hens,and accumulation dynamics of n-3 PUFA in egg yolk by dietary NS.In addition,metabolic pathways of EPA were identified by differentially expressed proteins using iTRAQ proteomics and bioinformatics methods.Exp.1 Determination of the nutritional components and prediction of ME for Nannochloropsis sp.Nutritional components of NS are,CP: 51.85%,EE: 8.01%,Ash: 6.17%,Ca: 0.29%,TP: 1.15%,Lys: 3.08%,Met: 0.96%.NS was also rich in ?-carotene(860 mg/kg)and n-3 PUFA(especially EPA,hardly DHA).Predicted ME by nutritional components was 2 808 kcal/kg(or 11.75 MJ/kg).Based on results of nutritional values,NS has a better nutrient than those of corn and soybean meal,can serve as a good protein feed resource with high energy and high protein as well as functional feed material as antioxidant and ingredient that can produce healthy meat,eggs and milk.Exp.2 Effects of dietary Nannochloropsis sp.supplementation on performance and egg quality for laying hensFour hundred and thirty-two healthy Lohmann laying hens aged 37 weeks with similar egg production rate and body weight were randomly divided into 6 groups with 6 replicates each group and 12 hens each replicate.Hens in control(CON)group were fed corn-soybean meal basal diets,and test groups hens were fed diets supplemented with 1%,2%,4%,8% NS(NSG)and 8% flaxseed(FSG),respectively.The experiment lasted 4 weeks.Results showed that: 1)Compared with CON group,all NSG and FSG group had no significant effects on performance,egg quality and yolk component for laying hens(P>0.05).However,albumen height(AH),haugh unit(HU)were significantly reduced after long time preservation(P<0.05),and the reduced levels of AH,HU in NSG8 and FSG group were higher than those in CON group.Yolk color score were higher than those in CON and FSG group(P<0.05)and peaked on about the 7th day in all NSG groups.2)Compared with CON group,yolk n-3 PUFA contents in NSG and FSG group were significantly improved(P<0.05),reduced n-6 PUFA(P<0.05)and ratio of n-6 to n-3(P<0.05).DHA and total n-3 PUFA content were highest in NSG8 group,reaching 111.62 mg DHA and 148.59 mg total n-3 PUFA per egg.Maximum DHA,total n-3 PUFA,and LC-PUFA levels were all observed at d 13 of NS supplementation.3)Sensory evaluation test showed scores of yolk color and albumen elasticity in NSG8 group were both higher than those in CON and FSG group(P<0.05).However,scores of yolk fishy smell and hardness were also higher than those in CON and FSG group(P<0.05).Egg preference study showed most consumers preferred the yolk color and egg mouth feel of NSG8 group,while the “fishy” off-flavor might influence the yolk or albumen flavor and odor.Finally,more than half of panelists chose NSG8 egg taking overall into consideration and overall sensory quality was not influenced.Exp.3 Effect of dietary Nannochloropsis sp.supplementation on hepatic protein expression in laying hensOne hundred and forty-four healthy Lohmann laying hens aged 37 weeks with similar egg production rate and body weight were randomly divided into 2 groups with 6 replicates each group and 12 hens each replicate.Hens in control(CON)group were fed corn-soybean meal basal diets,and test groups hens were fed diet supplemented with 4% NS(NSG).The experiment lasted 4 weeks.The livers were removed after slaughter.Then proteomics analysis of livers was performed using the iTRAQ method.Results showed that a total of 205 differently despressed proteins were identified in liver between CON and NSG4 groups,of which 88 proteins up regulated,meanwhile,117 proteins down regulated.Through the analysis of the differently proteins KEGG pathway,the enriched 8 related metabolic and signaling pathways were obtained.Peroxisome proliferator-activated receptor(PPAR)signaling pathway is an important signal pathway and connected other metabolic processes.Fatty acid,eicosanoid,etc.could be used as ligands of PPAR?.PPAR? forms a heterodimeric complex with the retinoid X receptor(RXR)to regulate the expression of genes related to fatty acid transport,oxidation and degradation in the process of fatty acid metabolism.The proteins of corresponding functions were expressed and involved in a series of process related to fatty acid metabolism in laying hen's liver.Quantitative analysis of differently depressed proteins showed that expression of ovomucoid and ovalbumin was both down regulated in liver,which may explain in molecular level the reasons of decrease in AH and HU,and short shelf life of NSG egg.