Managing to Prevent Grass Tetany

Is grass tetany a threat to your herd? It could be if you're dealing with cool conditions and lush spring forage growth. It is what we call “washy” grass. This new growth is very high in water and nitrogen. It can also be fairly high in potassium. Fields that have been fertilized with nitrogen may actually be even more imbalanced. The big problem is, these forages can easily be low in magnesium, and without adequate magnesium, livestock are susceptible to grass tetany. How Do You Protect Your Stock? Pastures with a good grass-legume mix, generally at least 30 percent, are normally a little better than monocultures of grass because legumes carry more magnesium than grasses. Grass tetany is generally more of a problem on fields that were grazed short last fall leaving very little or no dry matter behind to mix with the washy spring grass, and also in fields that have had early spring applications of nitrogen.  Once the forages start catching up to where they should be for this time of the year, and start maturing more, dry matter will increase in the forage, and nutrients will be more in balance. I’ve watched cows, after two or three days in a lush spring field, start going to fence rows looking for some dry matter. If they really are needing some dry matter and it is available, most will seek it out and consume it even

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2 thoughts on “Managing to Prevent Grass Tetany

  1. Thanks to Charlie Krauss for his comments. My wise dairy-farmer neighbor says this: “Always have dry available for cows when they are grazing.” I’ve noticed that my cows may graze on gorgeous grass/clover pasture and then see or hear me in the barn; they return and fill up on hay which I fork out for them. Also, this reference–http://www.fao.org/docrep/006/AD236E/ad236e16.htm –suggests that dandelions may help provide Mg and Ca for cows. We watch our cows enter a new paddock and invariably–after checking out the borders–go first for dandelions.

  2. A hundred years ago, dairy farmers around here followed a practice that protected them from grass tetany and made their lives easier.

    Just as soon as there was green grass, they would let the cows out to graze after the morning milking. They gathered them for the evening milking. At night, they fed dry fodder in a dry-lot so they wouldn’t have to gather them for the morning milking.

    Lush grass during the day and dry fodder at night made a better balance.

    A lot of cattle illness boils down to eating too much of something good – too much clover, too much grain, too much milk, etc.

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