Risk of Tetany

This is the time of year we get warnings of the potential for grass tetany and the need to supplement magnesium in the mineral for prevention.  “Grass staggers” or tetany can cause significant losses, yet many producers have never seen or encountered the problem.  Symptoms are typically animals showing nervousness, lack of coordination, staggering, grinding teeth, labored breathing, followed by collapse, coma and death.  Symptoms can easily be missed resulting in dead animals, with a small window for treatment involving intravenous sources of magnesium and calcium.

Tetany is a metabolic condition of low blood levels of magnesium (and likely calcium).  There are a number of identifiable risk factors.  It is usually encountered on lactating cows on early rapidly growing cool season grass pastures after cool and rainy weather.  It is more prevalent for cows wintered on low magnesium feed as corn stalks or silage and much less of a risk if pastures contain a legume as alfalfa and/or the pasture has considerable old growth grass along with the new grass.  Fertilizing with nitrogen or potassium increase the risk.

It has become accepted to prevent problems, provide supplemental magnesium on a daily basis during the risk period through Mg fortified mineral mix or supplement. Magnesium sources are not very palatable, so mixes or supplements must be formulated to be readily consumed .   Since low sodium levels contribute to low blood levels of magnesium and calcium, ready access to salt (loose preferred) is also important.