Effects of Dietary Rare Earth Chitosan Chelate on Performance, Egg Quality, Immune and Antioxidant Capacity, and Intestinal Digestive Enzyme Activity of Laying Hens

Rare earth chitosan chelate salt (RECC) is a potential feed additive and is a product of the chelation effect between rare earth ions and chitosan. This research study aims to explore the effects of dietary RECC on performance, egg quality, intestinal digestive function, and the immune and antioxidant capacity of laying hens in the late phase of production. A total of 360 56-week-old Dawu Jinfeng laying hens were randomly allotted into four treatment groups with six replicates per treatment and 15 birds per replicate. The laying hens were fed the basal diet supplemented with, respectively, 0 (control: CON), 100 (R1), 200 (R2), and 400 (R3) mg/kg for 8 weeks. Dietary RECC significantly improved average daily feed intake (ADFI) and average daily egg yield in both linear and quadratic manner (p < 0.05). In addition, albumen height and HU were improved significantly (p < 0.05) in a dose-dependent manner of RECC. In addition, a significant decrease (p < 0.05) in serum TP, IgA, and MDA for the R1 group and IgG in the R2 group were notable, while the increase in serum TP and decrease in T-AOC were found for R3 dietary group compared to CON (p < 0.05). The level of intestinal IL-2 and TNF-a was decreased by dietary RECC (p < 0.01). The activities of the digestive enzyme (a-Amylase, lipase, and Trypsin) showed a quadratic change with an increase and then decrease in response to increasing dose of RECC, 200 mg/kg RECC significantly increased the activity of lipase and Trypsin (p < 0.01). Supplementation of dietary RECC at low doses compared to higher doses impacted positive effects on the antioxidant capacity and immune function (p < 0.05). The utilization of RECC as a feed additive in the diet of aged laying hens exerted beneficial effects on egg production, albumen quality, humoral immunity, inflammatory response, and activity of digestive enzymes. Thus, the regulation of antioxidant capacity and duodenal function via increased enzyme activity and immune and inflammatory response were critical to the improvement of laying performance and egg quality in aged hens. The optimal supplemental dose is 100-200 mg/kg.