Dairy farmers must be wary of grass tetany at this time of the year, as too often, the only sign of grass tetany is when the animal is found dead in the field.
Grass tetany, which is also known as hypomagnesemia, is an acute magnesium deficiency in the blood of lactating cows, which is potentially fatal if it not treated promptly.
Magnesium is crucial for the nerves and muscles to function properly and if it comes under pressure, it will quickly affect the movement and temperature of the animal.
Early signs of grass tetany will be: the animals becoming excitable, nervous and unsteady on their feet, which can quickly evolve to cows being unable to stay up and falling over with heart failure and death quickly resulting.
Grass tetany
Grass tetany often arises from poor feed intake, cold and wet weather, and stress, as well as high potash applications in the springtime, which can also cause reduced uptake of magnesium.
Treatment of tetany would involve the administration of magnesium sulphate being carried out as soon as possible.
Ideally, the best treatment is the immediate administration of magnesium sulphate intravenously, usually combined with calcium to prevent concurrent hypocalcaemia (milk fever).
However, as we all know, prevention is better than cure, and it is also a cheaper way of limiting the number of tetany cases on your farm.
Farmers should try and avoid high-risk pastures to limit access to lush, rapidly growing pastures particularly in early spring, so cows should be gradually introduced to grass to allow their metabolism to adjust.
A magnesium treated not should be supplemented daily, as animals cannot store magnesium in the body, and a constant supply is critical during the shoulders of the grazing season, when risk is high.
The supplementation of magnesium blocks/licks out in the field or in the shed to ensure adequate levels of magnesium, calcium and other essential minerals is also important.
Another effective way of ensuring cows are receiving their nutrients is to supplement magnesium compounds in the drinking supply.
Supplementing hay or well wilted silage will slow down the digestion process of the animal and will allow for better absorption of magnesium in the diet.
It is best to implement a couple of these measures to reduce the risk especially during the September/October period when risk is at its highest.
