Spring brings life to everything around us - from crops being planted, to flowers blooming, and livestock ready to roam the pastures. However, there is one concern that arises - is the grass ready? Are my cattle at risk for grass tetany?
What is Grass Tetany in Cattle?
Grass tetany, a condition caused by low magnesium levels in cattle’s blood, is more prevalent in the spring. This occurs when cattle start grazing on young, lush grasses that are rich in potassium. But why does this matter?
High levels of potassium hinder magnesium absorption, leading to a decrease in magnesium levels. This is why it is crucial to ensure that cattle have easily accessible forms of magnesium during the spring, in order to prevent grass tetany.
To prevent grass tetany, here are five things you need to know.
5 Must-Know Facts about Grass Tetany in Cattle
1. Cool-season grasses are most likely to cause grass tetany.
Certain grasses pose a serious threat to your cattle’s health, particularly in the spring. Cool-season grasses like crested wheatgrass, bromegrass, bluegrass and timothy grasses are notorious for their high potassium levels, which can lead to grass tetany.
But it’s not just these grasses you need to watch out for – cereal grasses like wheat grass, rye, and oats can also contribute to tetany. In the winter, wheat pasture poisoning is a form of tetany that mostly affects cattle in Texas and Oklahoma. Wheat pasture poisoning is caused not just by a lack of magnesium, but also by a shortage of calcium. Wheat grasses with high potassium can also disrupt calcium absorption.
Additionally, pastures fertilized with nitrogen and potassium can increase the risk of grass tetany. That’s right, the very nutrients we often provide to support healthy pasture growth can actually hinder magnesium absorption in cattle.
To minimize the risk of grass tetany, experts recommend waiting until grasses reach a height of 8-10 inches before allowing your cattle to graze. As grasses grow, the potassium levels will decrease, while magnesium becomes more readily available. It’s a simple yet effective way to protect your livestock from grass tetany.
2. Grass tetany is more common in lactating cows.
Grass tetany is more common, especially in older lactating cows or those in late gestation grazing on lush spring forages. These cows already have limited magnesium reserves in their bodies. And when you add the extra strain of lactation and gestation, it only worsens the magnesium nutrient deficit. Lactating cows and cows in late gestation should be frequently monitored and provided a high magnesium mineral to help prevent incidences of grass tetany.
3. Grass tetany can be fatal.
Grass tetany is a silent killer that strikes suddenly, with the first symptom often being a dead animal. Other common symptoms that can occur include excitability, lack of coordination, muscle twitching, convulsions, comas and excessive salivation.
Weather can also play a factor in grass tetany. On cool, cloudy days between 40-60 degrees Fahrenheit, more instances and symptoms of grass tetany typically occur.
4. Salt can play a role in grass tetany prevention.
Discoveries made by British scientists in the 1930s revealed that salt has the potential to prevent grass tetany.
The absorption of magnesium in the rumen relies on sodium. While forages naturally contain sodium, a sudden freeze or frost can lead to the drying out of young forages, resulting in a sodium deficiency. To combat this, it’s highly recommended to offer free choice salt on every pasture during the spring season.
However, it should be noted that simply providing salt blocks isn’t enough, as cattle won’t receive the necessary amount of salt from a block alone. Mineral containing high salt content and highly available trace minerals like magnesium is the best option to prevent tetany.
5. Treat grass tetany with an IV injection of magnesium-calcium. Prevent grass tetany with high-quality mineral.
If grass tetany is suspected, immediately consult with your veterinarian. Treatment of grass tetany typically involves an IV injection of magnesium-calcium and a mineral supplement with high levels of magnesium (10%) and calcium (15-20%).
To prevent grass tetany, offer a mineral supplement with highly available magnesium, calcium and salt. Aim for daily intake of 2-4 ounces.
Keep in mind that even if your forages have adequate magnesium levels, it’s still recommended to provide a mineral supplement. The magnesium in forage may not always be available to cows.
The bottom line is that before you turn your cows out to spring grass, increase the magnesium and calcium levels in their mineral to prevent grass tetany. Start early in February or March to allow cattle to store mineral reserves in their bones.