At this time of year in Victoria, grass tetany is potentially a major problem in cattle.
Since cattle with grass tetany often die suddenly, the first sign of grass tetany on your property may be a dead cow.
To establish the likelihood of grass tetany occurring on your property it is worth considering some of the main risk factors.
Cattle contracting grass tetany are associated with immature, rapidly growing, grass-dominant pastures.
It is also linked with soils high in potassium, or with the heavy use of nitrogen or potash fertilisers.
Older, fatter cows soon after calving are most likely to be affected, and grass tetany is most likely to occur during cool and cloudy weather.
After considering the risk factors, it is worth planning how you would prevent, and if necessary treat, an outbreak of grass tetany on your property.
Grass tetany occurs when blood magnesium levels are low, therefore is also known as hypomagnesaemia.
Cattle are unable to store magnesium, therefore as protection, magnesium supplements need to be given daily to cattle at greatest risk during periods of potential grass tetany.
Consider how you would supplement your herd, and whether it is by giving magnesium oxide treated hay, mineral licks, magnesium capsules or by some other means.
When cattle are affected clinically with grass tetany they display initial excitement, bellowing, muscle spasms, tetany and finally convulsions before dying.
Since grass tetany leads to the rapid death of cattle, the treatment of clinical cases is an emergency situation and veterinary assistance should be sought immediately.
A veterinarian will give a calcium and magnesium solution intravenously.
If a veterinarian is not available the calcium and magnesium solution should at least be given under the skin.
■For more information, go to: http://go.vic.gov.au/bmp8MD
—Dr Jeff Cave
district veterinary officer