Rice straw for ruminants: processing technologies, nutritive value, feeding responses and environmental trade-offs

Abstract

Rice straw is an abundant roughage resource for ruminants, but low crude protein, lignified and silicified cell walls, and limited fermentable energy constrain intake and nutrient utilization. This critical review synthesizes processing technologies, nutritive value, feeding responses and environmental trade-offs, drawing on recent literature and a descriptive evidence map of 10 representative in vivo studies, predominantly from 2024 to 2026. Physical processing improves handling and ration mixing but has limited effects on structural recalcitrance. Urea ammoniation supplies non-protein nitrogen, while alkaline treatment increases fibre accessibility; recent buffalo trials report improved intake, digestibility and microbial nitrogen synthesis with urea–lime treatment. Ensiling and co-ensiling preserve wet straw, with sugar sources and microbial additives supporting fermentation. Co-ensiling with complementary crops or residues has maintained growth in sheep and improved intake, fibre digestion and milk output in dairy cows under specific formulations. Fungal, microbial and enzyme-assisted treatments show potential to improve cell-wall degradation, although farm-scale feeding validation remains limited. Nutritional gains depend on the complete ration, particularly fermentable energy, protein supply and physically effective fibre. Recent lamb evidence illustrates this dependence: partial replacement of conventional roughage with fermented rice straw maintained performance, whereas greater replacement impaired digestibility and feed conversion. Environmental benefits are similarly conditional. Diverting straw from open burning and replacing conventional forage may reduce pollution and resource demand, but processing inputs, transport, storage losses, enteric methane and nitrogen excretion can offset these gains. Methane responses vary with treatment and diet, and reduced animal-level emissions do not necessarily establish lower emissions per unit of product. Contaminant testing remains essential because processing cannot eliminate elemental pollutants. Across the mapped studies, nutritional and productive responses were more frequently reported than safety, economics or whole-chain environmental outcomes. Current evidence supports processed rice straw as a partial roughage component in balanced diets, while its contribution to sustainable food systems depends on maintained animal output, safe feedstock and locally demonstrated environmental and practical benefits.