Low blood magnesium levels can be caused by either grasses low in magnesium levels, a nutrient imbalance that interferes with magnesium uptake or high levels of milk production. Grass Tetany can occur in all types of cattle; however is most common in mature lactating beef cows with nursing calves less than 2 months of age.
There are several factors that may influence the concentration or availability of magnesium. Rapidly growing plants have a high content of Potassium which which affects the uptake of magnesium by plants and animals. High nitrogen fertility levels may also reduce the magnesium uptake especially in soils high in potassium. Magnesium requirements for growing cattle are 0.1 percent of their diet on a dry matter basis and for lactating beef cattle 0.2 percent of their diet on a dry matter basis.
Since Magnesium is not readily available from body stores, it should be fed on a daily basis. A mineral supplement is generally the fastest and most certain method of preventing grass tetany. Magnesium is not stored in the body long, so daily consumption is important. Supplementation should begin 2 to 3 weeks before tetany is likely to occur. There are numerous commercial mineral supplements available on the market, but as I said intake is critical to the success of the mineral program. Some producers have elected to use Magnesium oxide as a high mag source, but often cows will not consume enough as magnesium oxide is very bitter.
The Crystalyx brand offers a cost effective means to deliver a balanced supplement to meet the magnesium requirements of your grazing herd. Crystalyx has a product called “Super Mag” which is designed to provide dietary magnesium at the levels we discussed and also provide a balance mineral program in addition to promote growth and reproduction in your cow herd. For more information on Grass Tetany or the Crystalyx line of supplements, stop by MHFC Livestock Supply.