Preventing Grass Tetany in Spring

Preventing Grass Tetany in Spring
As we look forward to warmer temperatures, cool-season pastures become lush green and grow quickly. This growth can result in challenging conditions for grazing cattle, primarily lactating cattle. Grass tetany (or grass staggers) is a metabolic disorder caused by cattle foraging on high moisture, low nutrient (magnesium (Mg)) grasses. Animals with this disorder find it difficult to eat enough dry matter to meet their nutrient requirements. It generally affects older lactating cows but can also be an issue in dry or young cows and in rare cases, growing calves.Symptoms of Grass Tetany Include:

  • Nervousness
  • Staggering
  • Spasms
  • Convulsions
  • Overall lack of coordination

Further, this condition can lead to decreases in milk production and death. If grass tetany is suspected, a vet should be contacted quickly as treatment can save affected animals.

Timing & Species:
Grass tetany usually occurs when pastures are green and lush in spring, but can also occur in fall or winter, when cool-season grasses or small grains begin to grow quickly. Usual suspects are orchardgrass, perennial ryegrass, timothy, tall fescue, bromegrass, Kentucky bluegrass, annual ryegrass, wheatgrass and small grains (wheat, oats, barley, triticale and rye). Another possible occurrence is cattle wintering on corn stover (or anything with low Mg levels). Elevated N and K levels usually increase risk of grass tetany by decreasing levels of Mg available.

Management Tips to Help Prevent Grass Tetany:

  • Add legumes. Increasing legume content of pastures with clover (or alfalfa) can offset low Mg due to higher Mg levels in these species.
  • Refrain from placing cattle in recently fertilized fields or where significant amounts of manure have been applied (higher N & K levels tie up Mg)
  • Test soil and forage. If low Mg levels are suspected, testing soil and/or forage can provide insight into possible problems.
  • Use high Mg supplement. Animals should be fed a high Mg supplement or free-choice mineral (containing 8-12% Mg). Mg may be added to a protein or liquid supplement, grain mix or silage.
  • Handle affected animals gently. Treatment of cows in early stages of grass tetany can be effective, but animals should be handled gently to produce the least amount of stress possible. Corralling or roping can cause stress that may lead to death.

Reference: University of Kentucky, 2014; Purdue University

I’d Like to Add Legumes to My Pasture
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