While researching natural sources of antibiotics for cattle, scientists with the USDA Agricultural Research Service discovered that hops helps cattle gain weight.

“On the right diet, adding hops to feed can help cattle gain weight,” said ARS microbiologist Dr. Michael Flythe. “This would reduce the amount of feed required and decrease expenses for producers.”

Flythe, along with fellow researchers Isabelle Kagan and Glen Aiken, made the accidental discovery at the agency’s Forage Animal Protection Research Unit in Lexington, Kentucky. Flythe said he has been studying natural alternatives to synthetic antibiotic additives to cattle feed for 16 years.

He found that the cones of the hops plant are rich in bitter acids that act as natural antibiotics. One of his research assistants pointed out to him that the cows also experienced a bump in weight, he said. 

“Where they really shine is in finishing rations,” Flythe said. “In a mostly starch diet.”

The bitter acids in hops helps control gut bacteria that breaks down protein in the rumen (the first of the cow’s four stomach chambers). The un-degraded protein is digested rather than it going out in its urine, he said.

“Hops make potent bitter acids (the stuff that gives beer its aroma),” Flythe said. “These alpha and beta acids also help prevent sub-acute acidosis and lactic acidosis.”

There is a downside to using hops in cattle diets, though. The problem is that the alpha and beta acids (bitter acids), which are in the same family as tannins, also kill beneficial bacteria in cows’ stomachs, he said.

“If the cow’s diet is mainly coming from cellulose (roughage) — it can cause issues in the cows’ ability to break down fiber,” Flythe said. “Normally, it can use cellulose for energy due to the bacteria in rumen.”

According to the USDA, adding surplus hops to cattle feed not only saves cattle producers money, but it could also provide a value-added income source to hops farmers.