Abstract
The search for natural alternatives to in-feed antibiotics is a central focus in sustainable poultry production. This study investigated the individual and combined effects of Sanguinarine (SA) and Achyranthes bidentata polysaccharides (ABPS), two bioactive compounds derived from Chinese herbs, on the growth performance and immune function of yellow-feathered broilers. A total of 1728 one-day-old female broilers were randomly allocated to 36 treatment groups in a 6 × 6 factorial arrangement, with factors being six levels of SA (0, 0.4, 0.5, 0.6, 0.7, and 0.75 mg/kg) and six levels of ABPS (0, 200, 300, 400, 500, and 600 mg/kg). Over an 8-week period, growth performance indicators, including average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR), were monitored. Immune status was assessed through relative weights of immune organs (thymus, bursa of Fabricius, spleen) and lymphocyte proliferation at 4 and 8 weeks of age. The results demonstrated that SA supplementation significantly improved ADG during the initial 0-2-week period, while its effects on ADFI and FCR varied across different growth stages. ABPS supplementation was most effective in reducing FCR throughout the experiment, with the optimal effect observed at 500 mg/kg. Regarding immune parameters, SA at 0.7 mg/kg yielded the highest relative immune organ weights and lymphocyte proliferation at 4 weeks, whereas 0.5 mg/kg was most effective for lymphocyte proliferation at 8 weeks. ABPS at 500 mg/kg consistently promoted immune organ development and lymphocyte proliferation. A significant synergistic interaction between SA and ABPS was identified for several key outcomes. This interaction influenced ADG and ADFI at 8 weeks of age, relative thymus weight at 4 weeks, and lymphocyte proliferation at both 4 and 8 weeks. Notably, the combination of SA at 0.5 mg/kg and ABPS at 300 mg/kg (A(3)B(3)) produced a marked enhancement in lymphocyte proliferation. In conclusion, dietary supplementation with SA, ABPS, or their combination can modulate growth performance and enhance immune function in yellow-feathered broilers. The effects are dose-dependent and can be synergistic, with the combination of 0.5 mg/kg SA and 300 mg/kg ABPS showing particular promise for boosting cell-mediated immunity. These findings support the potential of SA and ABPS as beneficial natural feed additives for antibiotic-free poultry production.