Garfield County Cooperative Extension

Grass Tetany or Wheat Pasture Poisoning? One in the Same

Rick Nelson Extension Educator, Ag/4-H & CED

Grass Tetany or Wheat Pasture Poisoning? One in the Same

Some cattle producers are thinking about turning pairs out on small grain pasture. Although that lush green pasture seems appealing, there are hidden concerns that producers need to remember when turning out cows.

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 either as a magnesium deficiency, because feed companies offer magnesium to prevent occurrence, but really it is excessive intake of potassium. Potassium and magnesium compete for the same absorption pathway. With three times the potassium competing with one magnesium, the percentage of potassium is greater, and that nutrient is more likely to 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.

Most of the time tetany will happen when cattle are on lush forages such as small grain pastures. While transitioning from winter to spring, nutrients, including potassium, are being cycled up from ground through the roots to support plant growth. When we have a few weeks of warm weather, those nutrients get moved up to the plant that is above ground, actively growing. But if a cold snap or cool weather sets in, growth pauses and 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 cows out on wheat or rye pasture.

Since tetany is a nutritional issue, it isn’t isolated to just the spring, it can occur in the summer when we turn cattle out to grass. Tetany is a global issue and impacts all ruminants who have an improper potassium:magnesium ratio.

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 so that forces 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 when the growing season can easily be disrupted will prevent the vast majority of issues.

Remember to check your cattle regularly when they are first turned out to new, green pasture. Grass tetany is treatable if it is caught early enough. Consult your veterinarian at the first signs of any tetany. The veterinarian will typically provide an intravenous solution of calcium, magnesium and glucose to get the cow back on her feet. Timing is critical, though as cows will likely die if not treated within 4-8 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 pasture and remain healthy.



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