Effects of dietary Astragalus polysaccharides on nutrient digestibility, immune-antioxidant indices, hair ultrastructure, and gut microbiota in weaned kittens

This study aimed to examine the effects of adding graded levels of Astragalus polysaccharide (APS) on apparent nutrient digestibility, immune and antioxidant status, hair ultrastructure, and intestinal microbiota in weaned kittens. Eighteen 2-month-old British Shorthair kittens were randomly divided into a control group, a 0.02% APS group, a 0.04% APS group, and a 0.06% APS group, with 4-5 replicates per group and one kitten per replicate. The experimental period lasted 28 d, and blood samples were collected on days 14 and 28. The results showed that, in terms of apparent nutrient digestibility, APS significantly improved the apparent digestibility of dry matter, crude protein, and phosphorus (P < 0.05). In terms of hepatic and related biochemical indices, APS significantly increased plasma albumin concentration (P < 0.05) and decreased creatinine and blood urea nitrogen levels (P < 0.05). In terms of immune parameters, APS significantly increased IgG, IgA, IL-6, and TNF-α levels and decreased IL-10 level (P < 0.05). In terms of antioxidant capacity, APS significantly increased total antioxidant capacity and superoxide dismutase activity (P < 0.05). In terms of hair ultrastructure, the 0.06% APS group significantly decreased cuticle scale height and hair shaft diameter and significantly increased scale length (P < 0.05). 16S rRNA sequencing showed that APS did not alter overall microbial diversity, but the 0.06% APS group was enriched with Olsenella and Anaerobutyricum. In conclusion, 0.06% APS can improve nutrient utilization, immune and antioxidant function, hair ultrastructure, and intestinal microbiota homeostasis in weaned kittens.