By Scout Nelson
As cattle are turned out onto lush, cool-season pastures, the risk of grass tetany increases. This condition is caused by magnesium (Mg) deficiency and can lead to severe health problems and losses. Preventing it begins with strategic mineral supplementation before turnout.
Grass tetany is a secondary magnesium deficiency commonly observed during spring grazing. Even if pastures contain adequate magnesium, high nitrogen (N) and potassium (K) levels in the forage can reduce the absorption of magnesium in the rumen. This is especially true for improved pastures fertilized with N or K.
Magnesium is critical for muscle and nervous system function. Symptoms of grass tetany include nervousness, twitching, decreased feed intake, staggering, and in severe cases, convulsions. Lactating cows, especially older animals, are at the highest risk due to increased magnesium needs.
“Grass tetany tends to occur when forages have low Mg, low calcium, and high potassium.” Forages with less than 0.15% magnesium, less than 0.4% calcium, and more than 2.5% potassium increased risk.
To prevent deficiencies, it is recommended to supplement a mineral containing 10-15% magnesium in a 4-ounce daily intake, along with calcium and salt. Avoid adding potassium to mineral mixes, as this may worsen the problem.
Magnesium oxide (MgO) is the most common supplement, but it is bitter and often avoided by cattle. To improve intake:
- Introduce high-magnesium mineral mixes weeks before turnout.
- Add 1 pound of corn or distilled grains per 50 pounds of mineral mix if consumption is low.
Salt also plays a vital role. “Salt is critical for Mg absorption,” especially because sodium helps maintain the balance needed for magnesium transport in the body. When supplementing through feed, always provide free-choice salt. If using free-choice mineral mixes, include salt in the mix to encourage proper intake.
These steps help protect cattle health and support a smooth transition to spring grazing.
Photo Credits:istock-simplycreativephotography
Categories: Nebraska, Livestock, Dairy Cattle