An Agricultural Research Service scientist may have found a way
to cut the amount of ammonia produced by cattle. To do it, he's using a
key ingredient of the brewer's art:  hops.

Cattle, deer, sheep, goats and other ruminant animals depend on a slew
of naturally occurring bacteria to aid digestion of grass and other
fibrous plants in the first of their four stomach chambers, known as the

The problem, according to ARS microbiologist Michael Flythe , comes from
one group of bacteria, known as hyper-ammonia-producing bacteria, or
HABs.  While other bacteria are helping their bovine hosts convert plant
fibers to cud, HABs are breaking down amino acids, a chemical process
that produces ammonia and robs the animals of the amino acids they need
to build muscle tissue, according to Flythe, who works at the ARS Forage
Animal Production Research Unit (FAPRU) in Lexington, Ky.

To make up for lost amino acids, cattle growers have to add expensive
and inefficient high-protein supplements to their animals' feed.

According to Flythe, hops can reduce HAB populations.  Hops, a natural
preservative,  were originally added to beer to limit bacterial growth.

Flythe put either dried hops flowers or hops extracts in either cultures
of pure HAB or a bacterial mix collected from a live cow's rumen. Both
the hops flowers and the extracts inhibited HAB growth and ammonia

Flythe and FAPRU plant physiologist Isabelle Kagan have completed a
similar project with more typical forage. They recently identified a
compound in red clover that inhibits HAB.  Results of that study were
published recently in Current Microbiology.

Flythe also collaborated with FAPRU animal scientist Glen Aiken on a
study in which hops had a positive effect on the rumen's volatile fatty
acid ratios, which are important to ruminant nutrition.