Cordyceps cicadae polysaccharide and plant extract as a potential antibiotic-free feed additive: effects on growth performance, antioxidant capacity, and cecal microbiota of Yandang chickens.

This study was conducted to investigate the effects of a composite of Cordyceps cicadae polysaccharide (CCP) and plant extract (PE) on growth performance, serum antioxidant status, and cecal microbiota of Yandang chickens, a Chinese indigenous breed, with the aim of evaluating its potential as a natural feed additive candidate for antibiotic-free poultry production. A total of 315 1-day-old healthy Yandang chickens were randomly allocated to seven groups: blank control, vaccinated control, antibiotic control, CCP group, PE group, low-dose combination group, and high-dose combination group. Supplementation with CCP at 50 mg/kg BW significantly increased average daily gain (ADG) compared with the vaccinated control (p < 0.05); the high-dose combination did not differ significantly from the CCP group in ADG. All additive-treated groups significantly elevated serum total protein and albumin levels while reducing creatinine content (p < 0.05). The CCP group and high-dose combination group significantly increased serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities, and markedly decreased malondialdehyde (MDA) content (p < 0.05), with the high-dose combination showing the strongest antioxidant activity among all treatment groups. Cecal microbiota analysis revealed that the high-dose combination significantly increased the relative abundance of Bacteroidetes, a phylum known for its capacity to degrade complex polysaccharides. PERMANOVA based on Bray-Curtis distance revealed significant differences in overall microbial community structure among groups (p = 0.001). In conclusion, CCP supplementation was associated with improved growth performance, while the CCP-PE composite, especially the high-dose combination, enhanced antioxidant capacity and modulated cecal microbiota in Yandang chickens under the conditions of this study. The high-dose combination exerted the optimal comprehensive effects on antioxidant capacity and intestinal flora, and may be considered a promising natural feed additive candidate for antibiotic-free poultry production.