New USDA research shows that lactating cows may not need as much dietary protein as you think.

A typical lactating-cow ration contains 18 percent to 19 percent dietary protein. However, researchers with the agency’s U.S. Dairy Forage Research Center in Madison, Wis., have found that the optimal level may be closer to 16.5 percent. Lowering dietary protein to this level minimizes nitrogen output in urine without compromising milk production, says Glen Broderick, a dairy scientist at the center.

In fact, if U.S. dairy cows were fed just 1 percent less dietary protein, it could reduce urinary nitrogen output by about 60,000 tons per year, Broderick says.