Lowering the amount of crude protein in a dairy herd’s diet can save on feed costs while decreasing excess nitrogen and ammonia emissions. And it doesn’t have to adversely affect milk production, says Larry Chase, Cornell University Extension dairy nutritionist.

Chase proved all those points while working with two New York dairies – Herd A with 400 cows and Herd B with 700 cows by the time the eight-month trial ended.

Crude protein was reduced by about 1 percentage point for Herd A, from 17.5% to 16.6%, and less than that for Herd B, from 17.7% to 16.9%.

“The first herd we fed more corn silage and less haylage. Why? It didn’t have enough haylage to make it through the year. We took out some of the soybean and replaced part of the steam-flaked corn, part of the bypass fat and some months we had high-moisture corn and some we didn’t. It was a combination of things to balance the ration,” Chase says.

The second herd also was fed more corn silage as a percent of the total forage because it, too, had a deficient haylage inventory. “In fact, it was so short that, even though we went with more corn silage, we had to go from 60% forage to 48% forage in that herd during the trial.”

Part of the reason was that the dairyman was expanding his herd, Chase says.

“In both cases, we made some changes – lowered some of the feed costs per cow per day. But, as I tell our people in New York, I don’t really care. To me the important number is income over feed costs.

“Income over purchased feed cost increased 89¢/cow/day in Herd A and 35¢/cow/day in Herd B. That’s a fair amount of money when you start adding it up with the number of cows.”

The dairies saw an increase in percent milk true protein, related to a decrease in ration fat levels and an increase in starch. A two-unit decrease in milk urea nitrogen (MUN) values reflects the cows’ improved nitrogen (N) utilization and less N excretion, making the low-protein diets an environmentally friendly move.

Data from 10 nutritionists or consultants, on Wisconsin, Michigan, Pennsylvania and New York herds fed low-protein total mixed rations, showed a number of similarities:

  • Most herds had high milk production, greater than 80 lbs/cow/day.
  • MUN values were consistently less than 12 mg/dl for all but one herd.
  • Most herds were fed high-forage rations – 55% or greater total forage.
  • Ration fat levels tended to be moderate while non-fiber carbohydrates and starch levels were in the higher range.
  • Corn silage was the main forage for all but one herd, which fed only grass silage.
  • Herds showed high N efficiency.

Challenges to lowering crude protein, according to a 2006 survey of feed industry people that Chase quotes, have to do with consistency and quality of feeding equipment and management as well as daily forage quality variations.

Other factors include: lack of on-farm forage dry matter determinations and use of this data to adjust quantity of feeds added to mixer wagons, herd grouping and ration strategies, an increasing level of soluble protein in home-produced forage, the rising use of baleage on some farms, accuracy of forage samples and forage lab analyses and limited availability of daily MUN values as a monitoring tool.

“Don’t get hung up trying to go to 16% or 15% or 14%. Think about the herd you work with. Can we lower it by half a point to a point? That might really be a big deal in many herds,” Chase advises.