Effects Of Different Selenium Source And Level On Performance,Egg Quality,Content Of Selenium And Blood Biochemical Indicators In Laying Hens

Selenium(Se),an essential nutrient element of the organism,is an important component of glutathione peroxidase and selenoprotein and presents some physiological functions in anti-oxidation,anti-aging,anti-cancer and immunity.The body is often in a"sub-healthy"state which was caused by environment and life stress,intense competition and other factors.Previous studies showed the daily Se intake of adult in China was 26-32ug,which was far away from there commendation(50ug)of Chinese Nutrition Society.In recent years,Se-enriched products have become a hot spot in scientific research.However,Sewith different sources and different proportion supplemented to the feed not only causes much blindness for its application in animal production,but also brings a lot of negative effects in the production of Se products.Therefore,this study was conducted to investigate the effects of Se sources and levels on laying performance,egg quality and serum biochemical parameters of laying hens,which aims at providing experimental basis for future development of effective nutritional strategies to product Se-enriched eggs.This experiment was a 2×2 factorial arrangement.Seven-hundred healthy Roma laying hens with twenty 21-week-old and similar laying rate were randomly divided into 5 groups with 6 replicates,each replicate has 24 hens.The hens in the control group were fed a basal diet,the four experimental groups were fed a basal diet with different supplements:(A)yeast selenium 0.3 mg/kg,(B)yeast selenium 0.5 mg/kg,(C)sodium selenite 0.3mg/kg,(D)sodium selenite 0.5mg/kg,respectively.(The analyzed values of Se content in experimental diets were 0.178,0.362,0.572,0.323,0.533 mg/kg,respectively).The results showed that:(1)significant differences were observed in the production performance of Roman laying hens with different Se sources and levels treatment in diets(P<0.05).Compared with the basal diet,diet supplementation with Se can significantly increases the egg production rate(P<0.05).Diet supplementation with yeast Se reduces the egg shelling rate(P<0.05),but has no effect on the ratio of feed to egg(P>0.05)relative to the sodium selenite treatment diet.Diet supplementation with 0.5 mg/kg Se with same sources had the tendency to decrease the ratio of feed to egg.There was no significant difference in the rate of death among the 5groups(P>0.05).These results indicate that diet supplementation with 0.3 or 0.5 mg/kg Se showed no adverse effects on Roman laying hens,while supplementation with 0.5mg/kg yeast Se has the superior effect on Roman laying hens production performance.(2)supplemented different Se sources and levels to the basal diet significantly affected the14 d egg shape index(P<0.05).Compared with the basal diet,diet supplementation with 0.5mg/kg Se reduces the egg shape index,but had no effects on egg quality.Furthermore,significant differences were observed in28 degg weight,egg shape index,egg shell thickness and egg yolk index(P<0.05).Diet supplementation with 0.5 mg/kg yeast Se decreases(P<0.05)the egg shape index,and supplementation with sodium Se reduces(P<0.05)the thickness of egg shell;supplementation with 0.3 mg/kg yeast Se decreases the egg yolk index.The weight of egg white was significantly higher than that of0.3 mg/kg sodium selenite group(0.3 mg/kg sodium Se)(P<0.05).The average egg weight of the other groups was significantly higher than that of 0.3 mg/kg sodium selenite group,and the increase of 0.3 mg/kg yeast was the highest.(3)Different Se sources and levels in the diet significantly improve the activity of antioxidant enzymes(P<0.05).Compared with the basal diet,Diet supplementation with Se can significantly increases the activity of total antioxidant capacity,glutathione peroxidase,superoxide and catalase(P<0.05),and decreases the content of malondialdehyde(P<0.05).No significant difference was found in serum albumin and total protein(P>0.05)in the 5groups,but has the tendency increases its contents(P>0.05).The addition of 0.5 mg/kg yeast Se had the best effect on antioxidant and biochemical indexes in laying hens.(4)Compared with the basal diet,the Se content in eggs was significantly increased with diet Se supplementation(P<0.05).We can included that the content of Se increased with the increase of the addition levels of yeast Se or sodium selenitem.The regression equation is:Y=0.761X+0.226(R~2=0.959,),Y=0.516X+0.286(R~2=0.827),respectively.Quadratic regression equation is:Y=-1.07X~2+1.020X+0.268(R~2=0.904),Y=X~2+0.716X+0.2678(R~2=0.953),respectively.There were no significant effects on cholesterol levels in eggs when diet supplementation with different Se sources and levels(P>0.05),but a tendency decrease cholesterol in eggs.In conclusions,diet supplementation with 0.5mg/kg yeast Secan significantly increases the Se content of the eggs,improves the performance and egg quality,but reducesthe cholesterol content of the eggs.