Ammoniation of low-quality roughages for dry-season ruminant feeding: a review

Seasonal feed scarcity remains a major constraint to ruminant production in tropical and semi-arid regions, where low-quality crop residues and mature forages dominate dry-season diets. Ammoniation, using anhydrous ammonia or urea-based treatment, represents a practical approach to improving the nutritive value of these resources; however, its mechanistic basis and system-level implications have not been comprehensively synthesized in recent literature. This review integrates evidence published between 2015 and 2025, complemented by foundational studies, to examine the biochemical mechanisms, nutritional responses, and production- and environmental-level outcomes of ammoniation in tropical livestock systems. Ammonia-induced disruption of lignin-carbohydrate linkages enhance fiber accessibility and nitrogen availability, generally resulting in increased intake (10-40%), improved digestibility (5-20% units), and enhanced rumen fermentation. These changes are generally associated with improved animal performance, although responses depend on the synchronization of nitrogen release with fermentable energy supply and overall diet composition. At the system level, improved feed utilization may reduce emission intensity and promote the use of locally available biomass, supporting climate-smart livestock production. However, variability in treatment conditions, potential nitrogen losses, and adoption constraints remain important limitations. Emerging approaches, including integration with biological treatments and digital decision-support tools, offer potential to improve consistency and scalability. Overall, ammoniation remains a relevant strategy for enhancing feed utilization, productivity, and environmental performance in tropical ruminant systems.