Urea toxicity in ruminants: from feed to fatality

Urea is a colourless, crystalline, and hygroscopic chemical compound that is commonly used as a source of non-protein nitrogen (NPN) in ruminants due to its low cost and availability. Urea itself is not a source of amino acids; however, urea is digested in the rumen through the action of urease-producing bacteria and converted to ammonia. Ammonia is then utilized by rumen microbes, which use energy from carbohydrate digestion to produce microbial protein, which becomes an important source of amino acids.