As we drive around the countryside, it is beginning to look a little more like spring with each passing day. The weather is warming, slowly and sporadically, and producers are letting their cattle out to pasture with newborn calves at their side. Although lush green pastures look appealing it’s important to remember the risks of grass tetany this time of year.
Grass tetany, also referred to as hypomagnesemia, is caused by low levels of magnesium in the bloodstream all the while having an influx of potassium. Although older cattle on lush spring grass during early lactation are most susceptible to this disease, younger cattle as well those on dry lots are still at risk.
Springtime brings a higher risk of grass tetany because of the lush spring grass cattle are typically feeding on. Pastures are often very low in magnesium due to fast growth and cold soils this time of year. Potassium is taken up more readily in spring forages, also resulting in less magnesium. Additionally, spring is a popular time for calving. Lactating cattle need higher amounts of magnesium to support their milk production. If these needs are not met, milk production and the animal’s health dwindle. Older lactating cattle are most at risk because they cannot readily mobilize stored magnesium making them dependent on daily intake.
It is imperative to monitor recently pastured cattle for any symptoms. If caught in time, grass tetany can be treated with an intravenous (IV) magnesium solution. If gone untreated, death is likely. Early symptoms leading up to grass tetany are often overlooked; unless cattle are being closely monitored.
Common symptoms are:
- Reduction in milk production
- Muscle twitching
- Head thrashing
There are multiple prevention tips and considerations that are simple to incorporate:
- According to Iowa State University, pastures with grass at least 6 inches tall greatly reduce the risk of grass tetany.
- Integrate legumes, which are higher in magnesium, into pastures.
- Choose pasture ground with lower potassium levels.
- Provide cattle with a daily dose of a magnesium supplement. Iowa State recommends 30 grams of magnesium as the average daily intake for lactating cattle.
Dewell, Grant, and Steve Ensley. Hypomagnesaemia in Beef Cattle. Hypomagnesaemia in Beef Cattle, February 2016.