Effects of Different Selenium Sources on the Laying Performance, Egg Quality, Antioxidant, and Immune Responses of Laying Hens under Normal and Cyclic High Temperatures

SIMPLE SUMMARY: Heat stress is a major environmental stressor in livestock production, which seriously threatens the global livestock industry and causes huge economic losses. Strategies to address heat stress are mainly divided into three categories: genetic regulation, environmental regulation, and nutritional diet regulation. Among them, nutritional regulation is one of the current research hotspots. Selenium is an essential trace element for animals and humans. As a component of some anti-oxidant enzymes and selenoproteins, it plays an important role in improving anti-oxidation, anti-stress, immune function, and reproduction performance. This study investigated the effects of different selenium sources on the laying performance, egg quality, antioxidant, and immune responses of laying hens under different temperatures. The results showed that supplementation with different selenium sources can increase the egg yolk color, antioxidant capacity, and immune status, and can alleviate heat stress damage. Additionally, the effect of organic selenium is better than that of inorganic selenium. ABSTRACT: The aim of this study was to evaluate the effects of different selenium (Se) sources on the laying performance, egg quality, antioxidant, and immune responses of laying hens under different temperatures. In an 8-week experiment, a total of 480 44-week-old laying hens were randomly divided into 8 groups, with 6 replicates for each group and 10 hens per replicate, and fed with a basal diet (BK), basal diet with 0.3 mg/kg of Se from sodium selenite (SS), from Se yeast (SY), or from selenium-enriched yeast culture (SYC) under normal temperature (NT, 26 ± 2 °C) and cyclic high temperature (CHT, 26 ± 2 °C~33 ± 2 °C). CHT decreased the laying performance and serum levels of Se, immunoglobulin G (IgG), and interleukin-10 (IL-10), and significantly increased the serum free triiodothyronine (FT3), deiodinase-I (DI-I), and heat stress protein (HSPs) (p < 0.05). In addition, SYC increased the egg yolk color, and SS increased serum IgG level. SS, SY, and SYC reduced the level of interleukin-6 (IL-6) (p < 0.05). In conclusion, Se can increase egg yolk color, antioxidant capacity, and immune capacity under heat stress, and the effect of organic Se is better than that of inorganic Se.