Effects of Selenium Yeast on Egg Quality, Plasma Antioxidants, Selenium Deposition and Eggshell Formation in Aged Laying Hens

Simple Summary The depression of egg quality during the late stage of the laying cycle is one of the knotty issues in the poultry industry, which cause a great economic loss. Our study revealed that 0.45 mg/kg selenium yeast supplementation can alleviate the decline of egg quality in aged laying hens. In addition, organs Se levels and plasma antioxidant capacity were significantly higher with Se supplementation. Transcriptomic analysis identified some key candidate genes and potential molecular processes involved in selenium yeast's effects on eggshell formation. We inferred that 0.45 mg/kg selenium yeast has potential functions to alleviate the decrease in eggshell quality in aged laying hens to extend the laying cycle. These findings provide several new fundamental insights into improving egg quality in aged laying hens and extending the laying cycle. Internal egg and eggshell quality are often deteriorated in aging laying hens, which causes huge economic losses in the poultry industry. Selenium yeast (SY), as an organic food additive, is utilized to enhance laying performance and egg quality. To extend the egg production cycle, effects of selenium yeast supplementation on egg quality, plasma antioxidants and selenium deposition in aged laying hens were evaluated. In this study, five hundred and twenty-five 76-week-old Jing Hong laying hens were fed a selenium-deficient (SD) diet for 6 weeks. After Se depletion, the hens were randomly divided into seven treatments, which included an SD diet, and dietary supplementation of SY and sodium selenite (SS) at 0.15, 0.30, and 0.45 mg/kg to investigate the effect on egg quality, plasma antioxidant capacity, and selenium content in reproductive organs. After 12 weeks of feeding, dietary SY supplementation resulted in higher eggshell strength (SY0.45) (p < 0.05) and lower shell translucence. Moreover, organs Se levels and plasma antioxidant capacity (T-AOC, T-SOD, and GSH-Px activity) were significantly higher with Se supplementation (p < 0.05). Transcriptomic analysis identified some key candidate genes including cell migration inducing hyaluronidase 1 (CEMIP), ovalbumin (OVAL), solute carrier family 6 member 17 (SLC6A17), proopiomelanocortin (POMC), and proenkephalin (PENK), and potential molecular processes (eggshell mineralization, ion transport, and eggshell formation) involved in selenium yeast's effects on eggshell formation. In conclusion, SY has beneficial functions for eggshell and we recommend the supplementation of 0.45 mg/kg SY to alleviate the decrease in eggshell quality in aged laying hens.