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United States Department of Agriculture

Agricultural Research Service

Lohr (l), Gasbarre (c), Stout (r)

An Ounce of Prevention Equals Pounds of Milk

By Judy McBride
January 28, 1998

This year, Pennsylvania dairy farmer Larry Lohr will de-worm his cows twice instead of five times, as was his practice until 1997. The cows will get one treatment in spring after grazing all 19 of his paddocks and the second in late fall--for insurance. That should keep brown stomach worms from nibbling into his profits, thanks to an Agricultural Research Service study at Lohr's farm.

With the new approach in 1997, Lohr's cows averaged 3 more pounds of milk a day. Plus, their body weights stayed up and they excreted less nitrogen, a potential pollutant.

Lohr had suspected that worms were making the cows' milk production rates dip. So he collaborated on a 3-year study with ARS parasitologist Louis Gasbarre in Beltsville, Md., and soil scientist Bill Stout in University Park, Pa. The study was funded by a grant from USDA's Sustainable Agriculture Research and Education Program (SARE).

Lohr is one of a growing number of dairy producers trying to increase their bottom line by letting cows graze when possible, rather than cut, dry and store the feed and serve it up later. The practice lowered Lohr's feed costs, but his 19-day grazing rotation fit perfectly into the stomach worm's life cycle.

Gasbarre solved the problem by advising Lohr to have the cows "vacuum up" infectious larvae while grazing in each paddock at the start of the season. The worm treatment killed these ingested larvae before they could mature and deposit eggs in the feces-- which would re-infest the pasture.

An article about the research appears in the January issue of Agricultural Research magazine. The story is also on the World Wide Web at:


Scientific contacts: Louis C. Gasbarre, ARS Immunology and Disease Resistance Laboratory, Beltsville, MD 20705, phone (301) 504-8509, fax (301) 504-5306,; William L. Stout, ARS Pasture Systems and Watershed Management Research Laboratory, University Park, PA 16802, phone (814) 863-0947, fax (814) 863-0935,

Last Modified: 5/15/2017
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