It’s beginning to look more like spring each day, and producers are letting their cattle out to pasture with newborn calves at their side. As we admire the lush green pastures, it’s important to remember the risk of grass tetany this time of year.
Grass tetany, also referred to as hypomagnesemia, is caused by low levels of magnesium in the bloodstream with an influx of potassium. Older, early lactacting cattle on lush spring grass are most susceptible, while younger cattle and those on dry lots are still at risk.
Springtime brings a higher risk of grass tetany due to cattle feeding on the lush grass. Fast pasture growth and cold soils result in very low magnesium levels. Spring forages take up potassium more readily, which also causes low magnesium. With spring being a popular time for calving, lactating cattle need more magnesium for milk production. Without adequate magnesium intake, milk production and animal health dwindle. Older lactating cattle are most at risk; they rely on daily magnesium intake as they cannot readily mobilize stored magnesium.
It is imperative to monitor recently pastured cattle for any early grass tetany symptoms, as they are often overlooked. If caught in time, grass tetany can be treated with an intravenous (IV) magnesium solution. If gone untreated, death is likely. Common symptoms include; reduced milk production, restlessness, irritability, weakness, excitability, muscle twitching, stumbling, staggering, collapsing, and head thrashing.
Here are some simple prevention tips for your customers:
- According to Iowa State University, grass tetany risk is reduced when pasture grass is at least 6 inches tall.
- Integrate legumes into pastures, as they are higher in magnesium.
- Choose pasture ground with lower potassium levels.
- Provide a daily magnesium supplement; Iowa State recommends an average of 30 grams daily for lactating cattle.
Dewell, Grant, and Steve Ensley. Hypomagnesaemia in Beef Cattle. Hypomagnesaemia in Beef Cattle, February 2016.