Paper mulberry in animal nutrition: processing, host responses, and product quality

Paper mulberry (Broussonetia papyrifera) has attracted increasing attention as a local feed resource because it combines perennial woody biomass, protein-rich foliage and diverse plant secondary compounds. Its feeding value depends on plant part, harvest stage, processing method, fermentation quality, target animal species and dietary inclusion level. This review examines paper mulberry from feed composition and processing to animal responses, product traits and proposed mechanisms. Current evidence is strongest in ruminants, where paper mulberry silage or fermented feed has been associated with partial roughage replacement, maintained production and changes in rumen fermentation, antioxidant status, nitrogen utilization, milk fatty acids or meat quality under defined dietary conditions. Evidence in pigs, poultry, geese, fish and rabbits is more variable and suggests lower inclusion levels and stricter control of fibre, tannins and processing quality. Mechanistically, silage microbiota, tannin-protein interactions and rumen or hindgut microbial shifts are directly relevant to paper mulberry feeding, whereas nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1), nuclear factor kappa-B/mitogen-activated protein kinase (NF-κB/MAPK) and AMP-activated protein kinase-peroxisome proliferator-activated receptor-sterol regulatory element-binding protein 1 (AMPK-PPAR-SREBP1) pathways should be regarded as candidate explanations unless validated in target tissues. The main gaps include raw-material standardisation, fermentation-quality criteria, dose-response data, shelf-life endpoints and causal validation of proposed mechanisms.