Grass tetany or grass staggers is caused by low levels of magnesium in the blood. It is commonly observed in lactating cows grazing early, spring growth of cool-season grasses. Risk can increase with highly fertilized, permanent cool-season pastures or annual seeded grasses such as wheat or ryegrass.
AJ Tarpoff, Kansas State University Extension veterinarian, says older cows are at higher risk. He also emphasizes the symptoms can be fast acting and can lead to death.
“You can go out and check your animals one evening and everything looks fine,” he says. “The next morning you could have clinical issues, and you could have a couple animals actually succumb to the problem.”
According to Tarpoff, grass tetany symptoms include:
- Wobbling and staggering
- Continuous bellowing
- Straining to urinate
- Muscle twitching
- Potentially sudden death
Tarpoff encourages producers if they have a down animal or suspect grass tetany to contact their veterinarian immediately. The treatment process includes intravenous magnesium and calcium supplementation, with animals often responding quickly.
Jason Warner, K-State cow-calf specialist, explains extended periods of cool, cloudy days or days when there isn’t a lot of sunlight are ideal conditions for grass tetany to occur. This puts animals at a greater risk because of the weather’s influence on mineral content and levels in forages.
Warner adds that although grass tetany is primarily a spring condition, it can also occur later into the fall depending on forage and weather conditions.
Steps for prevention
Luckily, grass tetany is preventable. Tarpoff stresses the importance of prevention over treatment, as grass tetany is often a herd-based issue that requires proactive management.
Warner says the first step is understanding your forages and your overall cow herd mineral program.
“What is really important is understanding the product that you’re going to use, and what magnesium level is in that product,” Warner says. “Starting your supplementation program well in advance of when you think that peak risk-time period is going to be for those cows that are in question. Common recommendations of starting magnesium supplementation are about 30 to 45 days prior to anticipated time period of greatest risk for grass tetany.”
This will allow animals plenty of time to achieve a good level of consumption, get used to the product and start building up levels in the herd.
Magnesium oxide is the form that is most readily available and most rapidly absorbed. Warner says the challenge with magnesium oxide is it is quite bitter and can be unpalatable.
If a producer does not want to buy a mineral product that includes a high level of magnesium oxide, it can be purchased from a feed provider individually.
“If you just want to feed a base mineral that you’re already using and add magnesium as needed, you can do that,” Warner says, giving an example. “If you put out 50 lb. of a base mineral that’s got 2% magnesium in it … if you added 7.5 lb. of straight magnesium oxide to that 50 lb. bag of mineral, based on the magnesium concentration in that magnesium oxide, that will get you to about a 9% magnesium formula.”
Tarpoff and Warner agree producers should remain vigilant, understand their specific herd’s needs, and be prepared to quickly identify and treat potential cases.
“It’s something that we always have our eyes on, but [we’re] always planning ahead,” Tarpoff summarizes about grass tetany. “Prevention, management and proper supplementation is really important for this disease.”
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