Bloat in Beef Cattle

What is bloat?

Bloat is a risk when animals are grazing young, lush pasture, particularly if the pasture has high legume content (clover, medics or lucerne). Ruminant animals produce large volumes of gas during the normal process of digestion. This gas either is belched up or passes through the gastrointestinal tract. If something interferes with gas escape from the rumen, bloat occurs.

Natural foaming agents in legumes and some rapidly growing grasses cause a stable foam to form in the rumen. Gas is trapped in small bubbles in this foam in the rumen and the animal cannot belch up the gas. Pressure builds up in the rumen causing an obvious swelling on the left side of the body.

Bloat in cattle

Signs of bloat

Cattle with bloat may display the following signs:

• distended left abdomen;

• no longer grazing;

• a reluctance to move;

• appear distressed – vocalise, eyes bulging;

• strain to urinate and defecate;

• rapid breathing – mouth may be open with tongue protruding;

• staggering.

In advanced cases the animal will go down. Death is rapid at this stage, and is due to the swollen rumen compressing the lungs, interfering with breathing and tissue oxygenation, and obstructing blood flow.


When pasture is considered risky, bloat prevention options include the following:

• Restrict pasture intake by limiting grazing time or implementing strip-grazing.

• Fill animals on hay before turning onto pasture.

• Spray the pasture daily with pasture oil.

• Drench each animal twice daily with an anti-bloat preparation or oil.

• Apply anti-bloat preparations twice daily onto the flank.

• Add bloat oil into the water supply.

• Use anti-bloat blocks or licks.

• Use anti-bloat capsules .

• If hand feeding each day, add liquid bloat preventatives or products containing monensin to the feed.

Products containing monensin

Monensin changes the ratio of volatile fatty acids produced in the rumen. Its main use is to improve feed efficiency. It also decreases rumen methane gas production and reduces the amount of stable foam produced during fermentation, therefore it can be used to prevent bloat.

Important notes:

• Monensin is extremely poisonous to dogs, horses and other equines. Ingestion may be fatal. Care must be exercised to avoid accidental ingestion of monensin by these species.

• An overdose of monensin is toxic to cattle. Depending on the amount consumed, the signs of toxicity are:

• decreased feed intake

• poor growth

• depression

• death.

It is essential to follow label directions and accurately measure out the amount of monensin to add to feed on a weight basis. Thorough mixing and even distribution throughout the feed is essential.

• Never use monensin premix in combination with Elanco Rumensin® capsules.

• If dosing cattle with Elanco Rumensin® capsules in hot weather it is important to keep the capsules cool.