Enhancing Laying Hens' Egg Quality and Health with Se-Enriched Earthworm Hydrolysate

Developing new type of organic selenium (Se) holds promise for enhancing the quality of animal production and improving human nutrition. Earthworms can accumulate inorganic Se and convert it to organic Se. Consequently, we introduced inorganic Se (Na₂SeO₃) to earthworms, which were able to transform exogenous inorganic Se into organic Se through their Se enrichment and conversion capabilities. Subsequently, Se-enriched earthworm hydrolysate (SEH) was produced by utilizing earthworm hydrolase to decompose earthworm's own protein. Furthermore, laying hens were provided with a basal diet containing 0.1, 0.3, and 0.5 mg/kg of SEH and 0.3 mg/kg of Se-enriched yeast (SEY) for evaluation. Next, Se concentrations in eggs and tissues were quantified. The influences of SEH on laying performance in laying hens were investigated using performance terminology and measurements for poultry (NY/T 823-2020). Health levels were evaluated through analysis of serum biochemical parameters (high-density lipoprotein (HDL), low-density lipoprotein (LDL), alkaline phosphatase (ALP), total bilirubin (TBIL), urea, cholinesterase (CHE)), immune-related indexes (interleukin-2 (IL-2), interleukin-17 (IL-17), immuno-globulin G (IgG), immunoglobulin M (IgM)), and antioxidant capacity indicators (malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC)). Our study revealed that SEH and SEY significantly increased the Se levels of eggs on days 14, 28, 42, and 56, and Se in SEH is more readily enriched in eggs, compared to SEY. Additionally, SEH was found to enhance laying performance by reducing feed intake to egg mass ratio, improving shell thickness, yolk color, protein height, and Haugh unit. Furthermore, SEH was shown to improve the health status of laying hens by increasing HDL-C, boosting immune function through elevated IgM levels, and enhancing antioxidant capacity by increasing SOD levels. While SEY may enhance immune function by elevating IgM levels, it is associated with various adverse effects, including liver damage through increased ALP levels, inflammation via elevated IL-17 levels, and peroxidation due to an increase in MDA levels. In contrast, SEH has been shown to effectively decrease the feed intake to egg mass ratio, enhance egg quality, boost immune function, and improve antioxidant capacity in laying hens. Consequently, the utilization of SEH shows potential for the generation of Se-enriched eggs, enhancement of egg quality, and health of laying hens, offering substantial improvements over traditional Se sources like SEY.