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Producers should manage to mitigate grass tetany risk

by Wyoming Livestock Roundup

Producers are looking forward to warmer weather with the first week of spring. As temperatures rise, there are potential risks which can become problematic for producers and livestock.  

South Dakota State University (SDSU) Cow/Calf Extension Specialist Adele Harty explains the risk of grass tetany as well as how producers can manage and prevent it in a recent SDSU Extension newsletter. 

“Grass tetany is a metabolic disorder,” Harty explains. “It can be associated with the grazing of lush, growing green grasses throughout foraging pastures.” 

She adds, grass tetany causes a low concentration of magnesium in an animal’s bloodstream. This magnesium deficiency results in nerve impulse failure for livestock.  

Influential factors 

There are many influential factors which contribute to livestock’s susceptibility to grass tetany. 

A large factor is the age of livestock. Older, lactating cows with calves younger than two months have the greatest chance of encountering tetany, according to Harty, as mature cows don’t pull magnesium from their bones to stabilize blood magnesium levels like younger cattle.  

“Cows within a two month postpartum period also have a higher susceptibility to grass tetany,” she adds. “The increase of milk production requires additional calcium and magnesium. When a cow can’t keep up with higher mineral demand, it increases the susceptibility.”  

Additionally, Harty adds, producers don’t usually need to worry about steers, heifers, dry cows, cows with calves older than four months old or bulls having issues with grass tetany. 

Severe storms and weather, stress or other situations causing cattle to go off feed can heighten susceptibility to tetany.  

Harty explains, “Producers should also be aware of crude protein percentage of pastures or feed. Pastures with higher percentage protein can also be an influential factor regarding tetany.” 

Preventing tetany 

It’s a well known fact prevention is the best way to combat anything from disease to mineral deficiencies.  

Harty shares, “Prevention is the key when minimizing risks with grass tetany.”  

She continues, “Oftentimes, delaying turn-out until grasses are four to six inches tall can be successful. This reduces the occurrence of tetany, and it will provide pastures with rest and allow them to recover.” 

However, she adds, delayed turn-out is not an option for all producers.  

Harty says, “Producers unable to delay turn-out should utilize other management tools such as supplementation, providing hay or adding soluble minerals to water tanks.” 

“When producers are dealing with supplements, they should acknowledge the label and daily intake volumes,” Harty comments. “When providing supplements with high magnesium levels, producers should set out supplements several weeks before cattle begin grazing.” 

Harty notes palatability and adequate intake can be a challenge, so it is essential for producers to watch the cowherd and make sure the supplement is being utilized. 

Symptoms and treatment 

Death related to grass tetany can occur quickly after onset of symptoms, according to Harty. The symptoms cattle exhibit  may not be observed and progress over a span of four to eight hours.  

Harty recommends if producers see symptoms, incluing cattle grazing away from the herd, irritability, flank muscle twitching, wide-eye staring, muscular incoordination, staggering, collapsing, thrashing, heads thrown back or coma, they should act quickly. 

“There are treatment options available,” states Harty. “However, the effectiveness of treatment depends upon when it is administered.” 

Harty explains grass tetany can be treated with an intravenous (IV) dextrose-based preparation of magnesium and calcium, which can be attained from a local vet. 

She adds, “If producers can catch affected cattle soon enough, the possibility of cattle surviving is high. Treatment will not be effective if given after the cow affected by grass tetany has entered a coma.” 

                  Madi Slaymaker is the editor of the Wyoming Livestock Roundup. Send comments on this article to 

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