Battling bloat before death in livestock

With the flush of spring growth, bloat can become a distinct possibility.

Bloat occurs in cattle following the rapid consumption of lush, fast growing, immature, legume (clover or lucerne) dominant pastures. It is seen much less commonly on grass dominant pastures.

Bloat is caused by an increase in gas pressure within the rumen (paunch) as the feeds are fermented. The gas builds up in the rumen as small bubbles or foam that cannot be belched out when the animal chews its cud.

The first sign of bloat is a tight distended abdomen particularly on the left side. On occasions, the only indication of trouble is 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 from bloat can occur quickly, sometimes within 30 minutes of grazing pastures at risk, therefore the emphasis must be on prevention rather than treatment post the incident.

Hungry cattle should be prevented from gorging themselves on at-risk pastures, therefore, feed-out hay prior to introducing cattle onto possibly hazardous paddocks.

In addition, a range of treatments are available to help prevent bloat. These include bloat blocks, bloat licks, medicated water supply, drenching and pasture spraying. The suitability of each treatment approach varies dependent on the circumstances.

Many bloat deaths may actually be caused by pulpy kidney. Bloat slows down the passage of food through the gut allowing the pulpy kidney bacteria to multiply and kill the cow. All cattle should have an annual vaccination for pulpy kidney and other clostridia.

The best time to vaccinate is before a highrisk period such as spring.

For further advice contact your local veterinarian or your Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.