Non-protein nitrogen (NPN) products added to ruminant feed serve what primary purpose and what are the major ingredients?

• A. Provide vitamins
• B. Increase energy density
• C. Provide up to 40% of protein nitrogen requirements in the diet
• D. Reduce feed intake

Answer: (C)

Non-protein nitrogen products are used to supply nitrogen to rumen microbes so they can synthesize microbial protein, which the animal later digests and uses. This lets the diet meet part of the protein nitrogen requirement without adding true protein sources. In practice, NPN can contribute up to about 40% of the diet’s protein nitrogen, depending on energy availability and overall diet balance.

The most common ingredient is urea, which rapidly provides nitrogen for microbial growth. Other nitrogen sources used in NPN products include biuret (a slower-acting form) and inorganic ammonium salts such as ammonium sulfate or ammonium phosphate, which also help supply nitrogen and, in some cases, minerals.

NPN is not a source of vitamins or energy, and it should be used carefully to avoid ammonia toxicity; it works best when there is adequate fermentable carbohydrate and gradual introduction into the diet.