Greening spring pastures and growing cover crops are great opportunities for livestock to graze and get out of yards and dry lots. This fresh growth also allows animals to start putting back on condition that may have been dropped over the winter months. However, this is also the perfect set of conditions for a case of grass tetany.
Grass tetany is the result of low levels of magnesium in an animal’s blood stream. This mineral imbalance can be brought on by diet due to low magnesium levels in lush, newly growing grass. Because high levels of potassium interfere with the body’s ability to absorb magnesium, diets that are high in potassium (greater than 2.5%) are at even higher risk. Another mineral to look at is calcium. Calcium can act as a sort of buffer, limiting the impact of high potassium. Diets with calcium levels below 0.4% are considered low. In lactating animals, this drain on magnesium and calcium from milk production throws these imbalances off even more.
Animals with tetany issues will often graze separate from the rest of the herd, be irritable or excited, show muscle twitching especially round the ears and face, and walk with an uncoordinated, stiff, or staggering gait. Eyes may be wide and staring. In severe cases, animals will collapse, thrash around and can lapse into a coma leading to death.
To prevent tetany problems this spring, it’s best to wait till grass in pastures has grown to at least 6 inches high before grazing. Legumes like alfalfa or clover, are a good source of magnesium, so feeding or grazing pastures with a good mixture of grass and legume can help balance mineral demands and prevent possible problems. Keep an especially close eye on high milk producing or older animals, as these are the most likely candidates for a tetany issue.
While cultural practices can reduce risk, providing correct and adequate mineral supplementation may be the most fool proof solution. Sodium is important in the absorption of magnesium into the cell, so ensuring adequate salt is available and being consumed by the herd is important.
A sure prevention for grass tetany is feeding a mineral with supplemental calcium and magnesium included. Cattle should be consuming 3-4 ounces daily of mineral containing 10-13% magnesium oxide. This needs to be fed at least 30 days before grazing begins to ensure proper intake has been established. Most high magnesium mineral utilize magnesium oxide, which is bitter tasting and can reduce animal consumption. Mixing magnesium fortified mineral with salt into a complete package may help intake. If the 3-4 ounce target is still not being met, consider mixing the mineral with a highly palatable protein or energy supplement.
High magnesium mineral should be provided for animals until cool season grasses slow down growth and the levels of lush, fresh forage are reduced. This usually happens around mid-May.
Dealing with grass tetany in the spring is one of the annual cycles producers must deal with every year. However, with proper management, it doesn’t have to negatively impact your herd. Plan now to adjust grazing management or mineral supplementation for a tetany-free spring.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu .