Keep Grass Tetany at Bay

Pharmco territory has received much-needed moisture in the past couple weeks. Those rainy days, followed by sunshine, are welcome by farmers and ranchers alike. While this time of year is certainly a favorite for many, the spring growing season doesn’t come without important precautions…especially when it comes to protecting your cattle herd from grass tetany!

If you haven’t been hit by grass tetany, be grateful. The first sign of grass tetany in your herd is often a dead cow—or cows. Producers in our area who have been struck by tetany rarely forget the experience.

Once the deadly disease strikes, treatment is possible if you catch it early. But, that situation is rare. A better—and more economical practice—is prevention.

Most simply, grass tetany is caused by a magnesium deficiency. The deficiency can usually be attributed to an animal’s magnesium absorption being hindered by the high protein and potassium quality of early spring grasses. High nitrate levels in spring grasses and a lack of salt can also contribute to reduced magnesium absorption.

The deficiency is especially dangerous this time of year because lactating cows have a higher than normal need for magnesium. Providing your cows with a high magnesium mineral supplement is the most effective way to prevent grass tetany. To be effective, the mineral must be palatable; it does no good to spend money supplementing if the cows won’t eat it! Luckily, your Pharmco team can help.

Pharmco offers a variety of supplement options, including mineral tubs. Our products are created with palatability and nutritional needs in mind. Each of our store teams are well-versed in what works best for producers in specific areas, so contact your local store now—before the simple deficiency becomes a deadly problem.

Your local Pharmco team can also help you develop a big picture prevention plan by asking questions like:

  • Are salt and magnesium supplements readily available to grazing cows?
  • Are high potassium fertilizers being used on your pastures? If so, when are they applied, and can your turn-out date be altered?
  • Does your pasture contain a fair amount of high-magnesium legumes, or are your pastures crested wheatgrass heavy?
  • Can you control where or how your older lactating cows graze during times of greatest tetany risk?

Though grass tetany typically hits cows with calves at their side in early spring, it is possible for bulls or replacement heifers to be hit. Grass tetany can also become a problem in late summer or early fall after a heavy rain and rapid grass regrowth. For all these reasons and more, prevention and planning are key to avoiding loss from grass tetany.

You can minimize your herd’s risk to grass tetany, and your local Pharmco team can help! Contact your team today.


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36590 SD Highway 44
605-337-3374 / 800-683-3374

1250 East King Avenue
605-234-5209 / 800-258-1736

27768 317th Avenue

I-90 & Highway 45 South Side
East on Old 16