Beware of Bloat

By Dr Nik Cronin

I saw the first case of bloat in cattle for the season mid April - two young heifers died out of a mob of 22. They were grazing a mixed pasture including lucerne, chicory and grasses which was not ‘lush’ and abundant, but certainly fresh from the recent rain.

Bloat is caused by a build up of gas in the rumen – the main ‘fermentation’ stomach where primary feed digestion occurs. This process creates lots of gas, which under normal circumstances the animal can belch out. However, when feed is highly digestible a stable foam can form which may entrap the gas and prevent belching. Under these circumstances, gas can accumulate very quickly in the rumen. The associated rumen distension puts a huge amount of pressure on the heart and lungs, leading to cardiovascular collapse and death.

Clover dominant pastures are known for causing bloat, but as seen in this case, any fresh green feed that is highly digestible poses a risk. Mild daytime temperatures coupled with cool, moist nights, as we are starting to see this autumn, will promote vegetative plant growth and increase the bloat risk across the district.

So what can be done to manage the risk of bloat?

Prevention relies on being able to regularly deliver at-risk animals either an oil or synthetic surfactant which breaks down foam created by digestion, or an ionophore medication (monensin), which moderates rumen digestion to reduce gas production. These are both available in various commercial anti-bloat preparations and their effectiveness relies on regular (at least daily) delivery of an adequate amount of the active product, whether that be in water, feed or other method. Previously, bloat capsules containing monensin were available, but unfortunately these are not currently on the market.

If you have any further questions about managing the risk of bloat, please feel free to contact your local District Veterinarian on 1300 795 299.