Grass tetany is a magnesium deficiency of ruminants usually associated with the grazing of cool-season grasses during spring.
It is most prevalent among older cows in early lactation, but may also affect young or dry cows and growing calves.
Grass tetany occurs most frequently when cattle are grazing lush, immature grass with a high protein content but occasionally occurs when cattle are fed dry forages.
Frequently, clinical signs of grass tetany are not observed and the only sign is a dead animal.
However, there are telltale signs that can be seen under close observation.
Those would include animal grazing away from the herd, irritability, muscular twitching in the flank, wide-eyed and staring, muscular incoordination, staggering, collapse, thrashing, head thrown back, coma and death.
Grass tetany occurs most frequently in spring, often following a cool period when grass is rapidly growing, but can also be seen in the fall with new growth of cool- season grass or wheat pasture.
It is less likely in pastures where legumes are part of the pasture mix or with hay that contains legumes.
In areas where tetany frequently occurs, routinely feed cattle supplemental magnesium which increases blood magnesium levels and this will alleviate much of the grass tetany problem.
Magnesium is not stored in the body so it is important that each animal receives the proper amount of magnesium on a daily basis. Begin supplementation with magnesium before grass begins lush growth in the late winter and early spring and continue to feed magnesium until the threat of tetany has passed which occurs as the season progresses and grass growth slows.
Magnesium oxide is a good source of magnesium but it is not very palatable so it should be included in a very palatable energy or mineral supplement.
If you see animals with any of the symptoms discussed earlier in this article it is critical to treat the animal as quickly as possible.
Treatment results for tetany vary from excellent to poor depending on the clinical stage of the animal at the time of treatment.
If treatment is started within one or two hours after clinical signs develop, the results are usually a quick recovery.
However, in a large pasture it may be difficult to quickly identify sick cattle.
Pasture cattle should be observed at least twice a day when they are first turned on to new growth lush grass.
GIRARD —
