While driving through the pasture, you notice that one of your older cows is laying down and is having difficulty getting up. Another nearby has noticeable muscle twitches. Your first thought may be milk fever. However, this time of year there is a distinct possibility the problem may be grass tetany. Gary Naylor, Livestock Specialist with the Missouri Extension in Dallas County said the symptoms are very similar.
Grass tetany, is a condition resulting from low levels of magnesium in the cow's diet. Magnesium is an element, much like calcium, that is found in different amounts in soils throughout the Ozarks. Naylor said that soils in Dallas County generally have higher amounts than say soil in Greene and Christian counties, for instance. But the amount of magnesium in the soil is not the only factor raising the risk of grass tetany in your herd. Some plants take up magnesium from the soil better than others. Weather conditions also can play a part in the amount of this nutrient your cattle are getting from the grass they eat this spring.
Early in the season, grasses tend to grow quickly, which results in generally lower mineral uptake to the leaves. This is compounded during cool and damp conditions. Naylor said that grasses such as fescue and wheat pasture are, by nature, not as good at magnesium uptake. Legumes on the other hand are better at pulling minerals from the soil and making them available for grazing. In general, once plants begin to develop seed heads, in late May, the risk of magnesium deficiency drops significantly.
While nursing cows and older animals are more susceptible to grass tetany, even younger and healthier cattle are at risk if the conditions are extreme. There are several simple things you can do however to dramatically reduce the risk of this problem in your herd.
Simple soil tests or contacting your MU Extension office can tell you how much magnesium is in the soil of your grazing land. If you find the levels are low, application of a fertilizer with a higher magnesium content can help.
You also can assess the mix of forage in your pasture. If your grass is mostly fescue or you have your cattle on wheat pasture, be mindful that these grasses do a poor job of delivering magnesium to your herd, particularly in the spring. Pastures with more clover and other legumes can lessen the risk to your livestock.
Naylor suggested that the most sure way to guard against the onset of grass tetany in your herd is to provide magnesium supplement. While hay can help, remember that just like the grass, poor quality hay will not provide an effective hedge. Hays high in legumes are better.
In general, a cow should receive about 20 grams of magnesium per day. A variety of commercial supplements are available that help ensure your cattle get what they need. The simplest is raw magnesium oxide, but cattle find this rather unpalatable. Feed companies offer several alternatives that can be more convenient for you, and more palatable to your herd.
With a little information and some smart moves on your part, you can give yourself one less thing to worry about this spring.
