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Cutting Phosphorus in Dairy Cattle Feed Will Save Money, Help Environment

By Linda McGraw
July 16, 1999

Feeding dairy cows 20 percent less phosphorus could save U.S. dairy producers $100 million a year and improve water quality, according to an Agricultural Research Service dairy scientist in Madison, Wis. Excess phosphorus in water--runoff from fields--can boost algae and aquatic plant growth in streams and lakes.

Dairy producers have been overfeeding phosphorus to dairy cows. The National Research Council has recommended that dairy cows be fed about 3.8 grams of phosphorus per kilogram of feed dry matter. An average cow eats about 20 kilograms of dry matter per day.

About a year ago, ARS dairy scientist Larry D. Satter conducted a telephone survey of more than 30 dairy nutritionists, extension specialists, feed industry representatives and nutrition consultants. He concluded that, in practice, dairy producers were feeding an average of 4.8 grams of phosphorus per kilogram of dry matter. That’s 20 percent more than the typical dairy cow needs.

Over the last 20 years, ARS and other research institutions have conducted 13 studies of nearly 800 milk-producing cows eating both high- and low-phosphorus diets. From these studies, Satter concludes, contrary to common belief, that cows fed high amounts of phosphorous had no enhanced reproductive performance compared to animals fed low phosphorus.

Satter, based at the U.S. Dairy Forage Research Center in Madison will present these findings at the 1999 Four-State Applied Nutrition and Management Conference in LaCrosse, Wis., August 2-4. Conference attendees include dairy producers and representatives of the feed industry from Illinois, Iowa, Minnesota, and Wisconsin. California, Wisconsin, New York, Minnesota and Pennsylvania are among the top dairy producing states.

ARS is the chief scientific research agency for the U.S. Department of Agriculture.

Scientific contact: Larry D. Satter, ARS U.S. Dairy Forage Research Center, Madison, Wis., phone (608) 264-5353, fax (608) 264-5147,