Evaluation of optimal supplementation levels of sweet potato leaf and stem-based feed additives in broiler diets

This study investigated the effects of sweet potato by-product additives—control (no additive, CON), hot air-dried leaves (HL; 0.5% or 1%), hot air-dried stems (HS; 0.5% or 1%), and freeze-dried stems (FS; 0.5% or 1%)—on growth performance, meat quality, blood characteristics, growth hormone, and immune cytokine levels in broilers. A total of 280 one-day-old Ross 308 male chicks were randomly allocated to seven dietary treatments for 5 weeks, with five replicates per treatment and eight chicks per replicate. Supplementation with HL or HS 1% significantly improved body weight (BW) and average daily weight gain (ADG) (p < .05). HL treatments (0.5% and 1%) increased meat yellowness (b*) as well as crude protein and crude fat contents (p < .05). Hematological parameters were not significantly affected, although HL 1% supplementation elevated serum triglyceride (TG), calcium (Ca), and inorganic phosphorus (IP) levels (p < .05). Notably, HL and/or HS 1% increased circulating insulin-like growth factor 1 (IGF-1), interleukin 6 (IL-6), and interferon-gamma (IFN-γ) (p < .05). These findings indicate that supplementation with HL or HS 1% does not adversely affect broiler metabolism and may enhance growth performance and immune responses. Furthermore, the utilisation of sweet potato by-products as broiler feed additives offers a sustainable approach by recycling agricultural waste.