Bova Mag Minerals

Reduce grass tetany problems in your herd

These free choice minerals are designed to provide high levels of available magnesium to cattle that are at risk for grass tetany. Grass tetany is caused by low blood magnesium levels. This may be due to a simple deficiency of magnesium in the diet or to factors which reduce the efficiency of magnesium utilization by the animal such as high nitrogen and potassium levels in the forage.

  • Bova-Mag 5 contains high levels of available magnesium and trace minerals and vitamins
  • Bova Mag Breeder 5 contains high levels of available magnesium and trace minerals and vitamins as well as Zinpro Availa®4, which provides organic trace minerals

Key Benefits

beef cattle in pasture

Product Description


What Is Grass Tetany?
Hypomagnesaemia (grass tetany) is a common metabolic disorder in beef cattle caused by low magnesium (Mg) levels in blood. Tetany refers to a medical condition characterized by continuous spasm of skeletal muscle. Cows affected by grass tetany will show signs progressing from irritability, stumbling and thrashing, to coma and death. Grass tetany can effect any type or age of cattle during any season; but older cows in early lactation, grazing lush forage in the spring are most at risk. It is also common on finishing cattle and those raised in dry lots.

What Causes Grass Tetany?
Milk production is a constant drain on magnesium levels and cows need a daily intake of Mg to maintain adequate levels in the blood. In addition, older cows cannot readily mobilize Mg from bone stores, making them more dependent on daily nutritional intake.

Since cows have a daily requirement for Mg during early lactation, cows that go off feed can show evidence of grass tetany even though they are not grazing lush grass. Grass tetany can also be seen in finishing cattle, especially if finishing diets are marginal in Mg levels. Once an animal goes off feed they do not have any reserve Mg capacity and need daily supplementation.

How Can Tetany Be Avoided? Mature, lactating beef cows are most at risk for grass tetany. If turn out can be delayed until grass is at least six inches tall, the risk for grass tetany is greatly reduced. New grass growth in cool spring weather tends to have lower Mg levels, but incorporating legumes in the pasture will increase the Mg content of the forage in the spring diet.

Since cows cannot readily mobilize body stores of Mg to maintain healthy blood levels, they need daily Mg supplements, especially those feeding on lush growing grass. Dry lot or finishing rations should also be evaluated.

Cattle at lower risk for grass tetany (stocker calves or dry cows) should be placed on high-risk pastures. In the short term, prevention of grass tetany can be accomplished by supplementing Mg in the diet.

Feeding high magnesium minerals before placing cattle under conditions favorable for grass tetany can greatly reduce the chances of tetany occurring. Feeding between 1 0 and 12 grams per head daily of highly-available magnesium the month before tetany is likely to occur can help prevent the problem from happening.

Resource: Iowa State University
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