Bloat occurs in cattle following rapid consumption of lush, fast growing, immature, legume-dominant pastures such as clover or lucerne.

It is much less common on grass dominant pastures.

Bloat is caused by an increase in gas pressure within the rumen as feeds are fermented.

The gas builds up in the rumen as small bubbles or foam, which cannot be belched out when the animal chews its cud.

The first sign of bloat is a tight distended abdomen, mainly on the left side.

Or you might find many bloated animals dead in the paddock.

Death occurs due to the pressure of the rumen on the lungs and major blood vessels, leading to lung and heart failure.

Death can occur quickly, sometimes within 30 minutes of grazing dangerous pastures, so the emphasis must be on prevention rather than treatment.

To prevent hungry cattle gorging themselves on risky pastures, feed your cattle on hay prior to access to these paddocks.

In addition, a range of medications are available to help prevent bloat.

These include bloat blocks, bloat licks, medicated capsules, medicated water supply, drenching and pasture spraying.

The suitability of each prevention method varies depending upon the circumstance.

Many bloat deaths may actually be due to pulpy kidney.

Bloat slows down the passage of food through the gut allowing the pulpy kidney bacteria to multiply and kill the cow.

All cows should have an annual vaccination of "5 in 1" for pulpy kidney and other clostridia.

For further information on bloat or other health-related livestock issues please contact your local veterinarian or Agriculture Victoria veterinary or animal health officer. If you are located in NSW contact your Local Land Services.

Information is also available on the Agriculture Victoria website.