Scientists report that adding natural plant extracts to cow feed can reduce levels of ammonia gas by one-third while reducing the need to fortify feed with protein supplements.

The researchers shared the results of three studies undertaken to determine how adding plant substances called tannins to cow feed affects the emission of ammonia from dairy barn floors and farm fields fertilized with mixtures of cow manure and urine at the National Meeting and Exposition of the American Chemical Society.

Tannins apparently reduce urea production by allowing more protein to escape digestion in the stomach and enter the cow’s intestines, where it’s used to produce milk protein. Next on the agenda is research to determine whether tannins also can reduce emissions of methane gas from cattle production.