Purdue News

April 8, 2005

Specialist: Grass tetany-afflicted cows unsteady as they go

WEST LAFAYETTE, Ind. - Cattle are what they eat, and some bovines in Indiana aren't looking or acting very well this spring, said Ron Lemenager, a Purdue University Extension beef specialist.

"We've had a couple of cases of grass tetany reported in southern Indiana," Lemenager said. "Grass tetany results from a low blood magnesium level in cows. It usually happens in the spring when grass is starting to green up and grow, is high in water content, and low in minerals and other nutrients. When that occurs, magnesium is often one of the deficient minerals."

Grass tetany is most common in older beef cows that have just given birth to calves, Lemenager said. Lactating cows demand high nutrient intake, including magnesium. The mineral helps keep the animal's nervous and skeletal systems working properly. A cow with a magnesium deficiency becomes uncoordinated, has muscle tremors and staggers before going down.

The magnesium disorder can be fatal if not treated, Lemenager said.

"Grass tetany affects how the nerves fire and how the legs and skeletal structure function," he said. "Cows with grass tetany are going to be uncoordinated, and they're going to stagger. Some people refer to this as 'grass staggers.' A lot of times, these cows can go down and, if not treated, can die."

Other symptoms or behaviors cows suffering from grass tetany might exhibit include:

• Grazing away from the herd.
• Irritability.
• Muscular twitching in the flank.
• Wide-eyed and staring.
• Thrashing.
• Head thrown back.
• Comatose.

Most cattle producers do a good job of providing their animals with sufficient magnesium, Lemenager said.

"Grass tetany is easy to control by feeding a high magnesium-containing mineral mix," he said. "That can be an on-farm mineral mix that's about 25 percent trace mineralized salt, 25 percent magnesium oxide, 25 percent dicalcium phosphate and then 25 percent of something that increases the palatability, like ground corn or a dried molasses. We'd expect those cows to consume about four ounces of that mixture a day to manage grass tetany.

"The other thing producers can do is make sure that they leave hay out a little bit longer. It provides some dry matter and a little bit more nutrient-dense kind of feed at the same time that this new grass is low in nutrient profile."

Should a cow show signs of grass tetany, a producer must act fast.

"If you have a cow that is staggering, you need to have your veterinarian out as quickly as possible because the treatment for a cow that's got grass tetany is an intravenous infusion of a dextrose solution that's high in both calcium and magnesium," Lemenager said. "High calcium helps in magnesium absorption. Some producers might even feed a legume-type hay to these cattle because legumes tend to be higher in calcium and magnesium than grasses."

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Source: Ron Lemenager, (765) 494-4817, rpl@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
Agriculture News Page


Related Web site:
Purdue Department of Animal Sciences


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