Minerals are a crucial part of cattle health, development, and nutrition. Every rancher's mineral program will vary, but there is one mineral no rancher can afford to overlook: magnesium.
Each spring, cattlemen and women gear up for turnout, ready to let their herds graze fresh pastures. Cows with calves at their side eagerly chase the lush, green grass and savor the taste of spring. But while the fresh forage is a welcome sight, it also brings a silent threat for newly lactating cows: grass tetany.
Caused by a magnesium deficiency, grass tetany is a serious and often fatal condition affecting grazing cattle. As we prepare to turn out cows with calves at their side, while tackling persistent spring weeds, we must keep in mind the dangers of grass tetany. Understanding the risk factors, you can take proactive steps in prevention and management which lead to a healthier, more resilient herd.
What is grass tetany and why is it dangerous?
Grass tetany, also known as grass staggers or hypomagnesemia, is a metabolic disorder in lactating cattle resulting from a deficiency of magnesium in the blood. Adult, lactating cattle are more susceptible to grass tetany due to the loss of magnesium in the blood. Roughly 500 gallons of blood pass through the lactating cow's udder where nutrients, like magnesium, are absorbed. This is why we see grass tetany sickness and death highest among lactating cattle.
This condition primarily affects lactating cattle that are grazing on lush, fast-growing pastures, particularly in the spring. Oftentimes, when new green grass starts to emerge, cattle will concentrate on fresh growth due to its lush, tender, nutrient-filled taste. Yet, the new lush grass is low in magnesium. Magnesium depletion takes place due to the spring soil still being cool, causing potassium to be taken up more by the grass leaving magnesium in low uptake levels. This is where the danger lies.
The risk associated with grass tetany lies in its rapid onset and high mortality rate. Grass tetany can lead to paralysis and rigidity (muscle stiffness). Cattle affected by grass tetany may display symptoms such as muscle stiffness, restlessness, irritability, and staggering. As the condition progresses, cattle will collapse. If not promptly treated, affected cattle can succumb to the condition within hours.
The Role of Magnesium in Cattle Health
Magnesium is a vital mineral for cattle that plays a crucial role in a number of bodily functions, including nerve impulse transmission, muscle contraction, and enzyme activation. Unlike other minerals, the body does not store magnesium in large reserves, making continuous dietary intake essential. Magnesium is also a critical mineral for cattle growth, reproduction, and overall development of bones, teeth, and soft tissue.
Cattle primarily obtain magnesium from their diet. However, certain conditions, such as consuming grass high in potassium and nitrogen, but low in magnesium, can interfere with magnesium absorption. This imbalance often leads to the development of grass tetany.
Effective Prevention and Management Strategies
Preventing grass tetany involves several proactive measures. Providing a balanced diet that includes magnesium-rich supplements is crucial, particularly during high-risk periods. Ranchers can also offer high-mag minerals, blocks, and feed supplements to ensure adequate magnesium intake. Implement magnesium supplements at least two to three weeks prior to turning cattle out onto new, green pastures. If cattle are presently grazing, provide supplements before pasture green-up. Cattle need to intake around 0.6 oz. per day of magnesium (Mg).
Management of pasture quality is equally important. Avoid overgrazing and ensure a variety of forages to help maintain appropriate magnesium levels in the diet. In some cases, rotational grazing or introducing legumes into pastures can improve overall mineral balance. At spring green-up, it's always wise to wait until forages are 4-6" in height before turnout. Keep enough hay out for your cattle to supplement their forage needs, until they stop consuming the hay.
In the event of an outbreak, immediate treatment with magnesium supplements, either orally or via injection, can save affected cattle. Regular monitoring and quick response to any signs of deficiency are essential components of an effective management strategy. As always, consult your local veterinarian for the best safety protocols to establish for your cattle operation.
Timing for grass tetany is typically from mid-February through April, in the southeast. Remember, magnesium is not stored in the animal's body, so we must meet their magnesium mineral requirements. See this mineral guideline from the University of Tennessee for more mineral information.
Through herd health, you grow grass, pounds, and profit.
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