Effects of dietary chitosan oligosaccharides on the laying performance, egg quality and serum biochemical parameters of aged laying hens.

This study examined the impact of nutritional supplementation with chitosan oligosaccharides (COS) on the laying performance, egg quality, and serum biochemical markers of aged laying hens. A total of 192 aged laying hens with 80-week-old were randomly assigned to a baseline diet (CON) or a basal diet with 200, 400, or 800 mg/kg COS. Trial lasted 8 weeks. Compared to CON, the 200 mg/kg COS group showed numerical improvements in most parameters, but statistically significant enhancements were observed starting from 400 mg/kg. COS supplementation at 400 and 800 mg/kg significantly increased hen-day egg production, weight, mass, and improved feed conversion ratio (FCR: 2.52, 2.41, 2.24, 2.27 kg/kg egg mass for CON, COS200, COS400, COS800, respectively) compared to the CON group (P < 0.05). COS-supplemented groups showed increased egg quality, including thickness, strength, albumen height, Haugh unit, yolk color, and index (P < 0.05). Serum analysis showed COS supplementation decreased total cholesterol, triglycerides, and LDL-C while raising HDL-C (P < 0.05). COS-treated aged laying hens had higher total protein, albumin, and globulin and lower aspartate aminotransferase (AST) and alanine aminotransferase (ALT) compared to the control. Additionally, COS supplementation increased serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities and decreased malondialdehyde (MDA) levels (P < 0.05); these antioxidant indicators exhibited a dose-dependent rise from 200 to 400 mg/kg, reaching a plateau at 800 mg/kg (e.g., SOD: 116.4, 132.7, 141.8, 139.6 U/mL). COS groups showed improved immune function, with greater serum immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels (P < 0.05). The results showed that aged laying hens fed 400-800 mg/kg COS had superior laying performance, egg quality, lipid metabolism, antioxidant status, and immunological function, suggesting it could boost productivity and health.