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Serving: MO
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WATCH SPRING WEATHER: While the bright green grass is appealing to cows, there is a risk. Warm weather-cold weather cycles make potassium levels twice the normal amount in plants, and too much grazing by cows can lead to tetany.

Green grass and cows don’t mix

How to prevent grass tetany this spring.

The snow might be still be flying throughout much of the country, but it won’t be long before cattle producers will open the spring pasture gates. Although that lush green grass seems appealing, there are hidden concerns that producers need to remember when turning out their cows.

One of those concerns is grass tetany. Kevin Glaubius, director of nutrition at BioZyme Inc., based in St. Joseph, Mo., took time to answer a few questions about grass tetany to help producers prepare for spring and early-summer grazing.

1. What is grass tetany? What causes it, and what are the symptoms? Grass tetany is also called grass staggers, because when cattle become susceptible, they start to stagger around and will go down on their side. One of the first symptoms is general lack of coordination.

Most producers think of tetany as a magnesium deficiency, because feed companies use magnesium to prevent occurrence; but really, it is excessive intake of potassium. Potassium and magnesium compete for the same absorption pathway. Think of it like a funnel, where three potassium marbles are trying to get through the funnel at the same time as one magnesium marble. Since the percentage of potassium marbles is greater, that nutrient is more likely to go down the funnel and get absorbed before the magnesium does.

Tetany typically occurs in older animals rather than younger animals because of an inability to mobilize the magnesium from the bones. Mature cows will show signs long before a young calf.

2. Is there a time of year it is most prevalent? Is grass tetany found in every region, or does it confine itself to one geographic area? Most of the time, tetany will happen when cattle are on lush forages. While transitioning from winter to spring, nutrients, including potassium, are pumped up from the ground through the roots to support plant growth. When we have a few weeks of warm weather, those nutrients are pumped up to the plant that is aboveground and actively growing. But if a cold snap or cool weather sets in, growth pauses — but those nutrients remain in the plant. With those warm weather-cold weather cycles, the potassium levels can potentially become twice the amount they normally are, leading to tetany challenges when you turn your cows out around May 1.

Since tetany is a nutritional issue, it isn’t isolated to just the spring and summer when we turn cattle out to grass; it can also happen while feeding hay. In that case, we have what might be referred to as “winter tetany” or “wheat pasture poisoning”: when cattle are fed harvested winter feeds that are high in potassium.

Most of the country doesn’t have problems with it in the fall. However, it can be an issue — especially if producers fertilize in the fall.

Tetany is a global issue and affects all ruminants that have an improper potassium to magnesium ratio.

3. What are the best ways to prevent grass tetany? There is no perfect mineral for preventing grass tetany. If you have extremely high potassium level, it is important to realize that a higher percentage of magnesium doesn’t always mean it is better. Magnesium isn’t palatable, and cows will likely walk away from straight magnesium or minerals with slightly higher levels of magnesium.

Start increasing magnesium levels about two weeks before turning out to pasture, so you can gauge how much the cow might eat when she is turned out on grass. Remove all other sources of salt to force the cows to get salt from the mineral, if the bitterness of higher magnesium restricts intake to less than the restricted amounts.

Feeding a high-mag mineral during the high-risk periods, such as spring and fall, when the growing season can easily be disrupted, will prevent the vast majority of issues.

4. If an animal is diagnosed with grass tetany, how is it best treated? Remember to check your cattle regularly when they are first turned out to new green grass. Grass tetany is treatable if it is caught early on. Call your veterinarian at the first signs of any tetany. The vet will typically provide an intravenous solution of calcium, magnesium and glucose to get the cow back on her feet. Timing is critical, though; cows will likely die if not treated within four to eight hours after onset.

The key to preventing tetany is to provide the proper amounts of all nutrients. If you can keep your magnesium to potassium ratio in check, your cows should enjoy grazing green grass and keep healthy. BioZyme offers several supplements in its VitaFerm product line that are enhanced with magnesium to help prevent the onset of tetany. To learn more about these and other VitaFerm products, visit

Source: BioZyme Inc.

TAGS: Forage
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