What's New? HiMag Fescue
Forage specialist Glenn Shewmaker examines tall fescue in a test plot at the
ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho.
A hardy new grass called "HiMag" may help protect cattle, sheep,
and goats from an affliction known as grass tetany.
When ruminantsanimals with four stomachshave too little
magnesium in their blood, grass tetany can result. Also known as
hypomagnesemia, grass tetany causes an estimated $50 to $150 million in
livestock production losses each year in the United States.
Because it is unusually high in magnesium, the new tall fescue grass should
help protect vulnerable animals from magnesium deficiencies. Plans call for
HiMag seed to be made available to plant breeders this year.
Investigators Henry F. Mayland, who is with
ARS at Kimberly, Idaho; Glenn E.
Shewmaker, formerly with ARS and now at the University of Idaho; and David A.
Sleper and colleagues at the University of Missouri developed HiMag in a
cooperative effort that began in 1983.
As part of the HiMag collaboration, Shewmaker and Mayland scrutinized
mineral levels of hundreds of candidate forage plants. They did the work at the
ARS Northwest Irrigation and Soils Research Laboratory at Kimberly. HiMag had
up to 20 percent more magnesium than some of the other plants they examined.
And their greenhouse tests showed that levels of magnesium remained high in two
So far, HiMag has been tested not only in Idaho and Missouri, but also in
Utah, Texas, Arkansas, Georgia, Virginia, and New York, as well as in Canada.
Scientists recommend it for rain-fed pastures in eastern, southeastern, and
Pacific Northwestern states and British Columbia.
A Research First
The idea of breeding a high-magnesium forage grass to combat grass tetany
isn't new. But the ARS and University of Missouri researchers are the first to
accomplish that with tall fescue.
ARS grazing trials in Idaho with a dozen Angus and Angus-Hereford heifers
indicated that the cattle find the plant palatable and will make profitable
weight gains. When given a choice among HiMag and seven other tall fescues,
HiMag garnered a respectable third-place.
Such a reality check with four-legged customers is crucial: Plant breeders
elsewhere have learned the hard way that no matter how healthful a forage is,
animals may turn up their noses at it if they don't like the taste or aroma.
The grazing test included only tall fescues that were free of a troublesome
microbe known as an endophytic fungus. Cattle that graze on infected fescue may
not gain as much weight as they should and may also have reproductive problems.
Nevertheless, tall fescue is planted on more acres of American pastureland than
any other type of forage grass.
Grass tetany is often fatal. Symptoms include nervousness, convulsions, and
paralysis. Sometimes, potassium plays a role in the disease by outcompeting
magnesium for what are known as absorption sites in an animal's gut. That can
happen if hungry ruminants graze on pastures that have been overloaded with
high-potassium commercial fertilizers or potassium-containing manure.
Preventive measures include adding magnesium to drinking water or salt licks
or spreading it around the pasture with a fertilizer spreader. Each tactic has
drawbacks. Spiking trough water with magnesium, for example, works only if
animals will make the trip to the trough which may be a mile or so away.
They might choose instead to guzzle rainwater from a convenient puddle or
"A palatable, magnesium-rich forage," says researcher Shewmaker,
"is a better guarantee that the animals will get the right amount of this
essential nutrient."By Marcia Wood, Agricultural
Research Service Information Staff.
This research is part of Soil Quality and Management, an ARS National
Program described on the World Wide Web at
Henry F. Mayland is
at the USDA-ARS Northwest Irrigation
and Soils Research Laboratory, 3793 N. 3600 E., Kimberly, ID 83341; phone
(208) 423-6517, fax (208) 423-6555.
"What's New? HiMag Fescue" was published in the
April 1999 issue of Agricultural