Applications for the Dramas, Fairs and Festivals grants for this quarter are due in the Extension Office by May 1. If you have any questions or need an application form, please call the office at 340-799-4852.
Pocahontas Producers Spring Sale Schedule
Regular Sale – Saturday, May 23, 2 p.m.
Regular Sale – Saturday, June 20 – 2 p.m
Reducing the Risk of Grass Tetany
by Ed Rayburn
What is Grass Tetany?
Grass tetany, or hypomagnesmic tetany, occurs when Magnesium (Mg) levels in a cow’s blood are too low. This is caused by a low content or availability of Mg in pasture or hay which occurs when the forage is low in Mg or when the forage is high in nitrogen or potassium relative to Mg. The latter often occurs after heavy application of mineral fertilizers or manure. A plant’s Mg content is depressed in cold soil when there is inadequate phosphorus, a mineral necessary for Mg uptake by plants. Grass hay crops grown under cool, moist conditions, and those that have been rained on, often contain low levels of Mg and are at risk for causing winter tetany in beef cows.
Older cows, cows in early lactation, and especially old cows in early lactation, are most prone to grass tetany since Mg uptake decreases as cattle age, and since a cow’s Mg requirement is highest in early lactation. Cows in early lactation need a ration containing 0.20 percent Mg (dry matter basis) while they only need 0.12 percent Mg during gestation. Growing and finishing cattle need 0.10 percent Mg. When cows in early lactation are fed forages testing less than 0.20 percent Mg, also feed them a supplement of Mg oxide (60 percent Mg) in mixture with salt, other minerals, and grain. Insure that each animal gets about 2 ounces of Mg oxide (about 50 grams) each day. Commercial mineral mixes containing adequate Mg can do an excellent job reducing the risk of grass tetany.
Grass forage grown on soils testing low or medium in Mg may produce forages that are at high risk of causing grass tetany, especially when fertilized with nitrogen or potassium during cool, wet weather. The risk of grass tetany is reduced by the use of high Mg lime to increase soil test Mg when soil pH is low, and by applying potassium and nitrogen fertilizer in late summer or early fall. Early spring applications of phosphorous will cause no problems since phosphorous is needed by plants to take up Mg. Growing legumes in place of using nitrogen fertilizer helps reduce the risk of grass tetany. Supplementation with Mg oxide will help reduce the risk of grass tetany when cattle are fed forages low in Mg. Be sure to soil test hay meadow and pasture soils and apply recommended lime, phosphorous, and potassium in the fall. To optimize livestock nutrition and health, forage test your hay crops to learn when Mg supplementation is needed during the fall, winter, and spring.