<i>Astragalus</i> polysaccharide mitigates <i>Eimeria tenella</i>-induced damage in laying chicks by modulating immunity, inflammation, and intestine barrier

Astragalus polysaccharides (APS), the main active component of the traditional Chinese medicine Astragalus, exhibit immunomodulatory and antioxidant properties. This study analyzed the preventive and therapeutic effects of APS on chicks infected with Eimeria tenellaE. tenella and its impact on intestinal health. A total of 120 1-d-old Hy-Line Brown chicks were assigned to four groups (2 × 2 factorial): 1) Control (0 mg/L APS + 0 sporulated oocysts/chick), 2) APS (1,000 mg/L APS + 0 sporulated oocysts/chick), 3) E. tenellaE. tenella (0 mg/L APS + 5 × 104 sporulated oocysts/chick), 4) E. tenella + APS (1,000 mg/L APS + 5 × 104 sporulated oocysts/chick). The results showed that the addition of APS to the drinking water increased the average daily gain and body weight (day 25) while reduced feed conversion ratio in E. tenella-infected chicks (P < 0.05). APS mitigated cecal lesions (P < 0.05), decreased oocyst shedding (P < 0.05), lowered spleen index (P < 0.05), and elevated bursa and thymus indices (P < 0.05). Serum total protein and alkaline phosphatase activity increased (P < 0.05). Cecal tissue mRNA expression of IL-2, IgG, IgM, Claudin1, Claudin2, ZO-1, and Occludin were increased (P < 0.05), whereas IL-1β, TNF-α, and NF-κB were decreased (P < 0.05). APS enriched cecal f_Lactobacillaceae, g_Lactobacillus, g_Tuzzerella, g_Oscillospira, and g_UBA1819 (P < 0.05). Furthermore, the anticoccidial index (142.10) indicated low-level efficacy. In conclusion, APS alleviated E. tenella damage by modulating immunity, inflammation, microbiota, and intestinal barriers. Although APS demonstrated limited direct anticoccidial activity, its multifaceted protective effects suggest potential in the prevention and treatment of coccidiosis.