Bloat (frothy)

Bloated dairy cow

What to look for

  • Animals are often found dead with a very distended abdomen
  • If found before death: distended abdomen on the left side between the last rib and the hip bone very distressed, difficulty breathing if untreated, may die quickly
  • Cows can also have less severe forms of bloat that may depress milk production


Consumption of young, rapidly growing legumes, clover or lucerne. Bloat is usually caused by eating pasture species that are growing quickly and contain low fibre levels. Consequently, animals produce less saliva production which makes them more susceptible to bloat. Under certain circumstances, feeding on these pastures can lead to build up of foam in the rumen that prevents animals burping to remove the gas produced in the rumen.

Animals likely to be affected

Heifers are more likely to die of bloat than older cows. There may be breed differences in susceptibility, with Jerseys and crossbred cattle being more susceptible.

Other diseases with similar signs

Other causes of sudden death.

Confirming the diagnosis

  •  Sudden death of animals with very distended abdomens (this is only useful in diagnosis if the animal has died recently because all animals will “blow up” after death)
  • Recently introduced to pastures with a high clover or lucerne content
  • Characteristic foam in the rumen (but this only lasts for a few hours after death)


  1.  Move animals from the toxic pasture to a pasture with lower levels of clover or lucerne
  2. Provide supplementary feed such as hay or silage
  3. Animals that are mildly affected can be treated with a bloat drench. In advanced cases of bloat it is often difficult to administer treatments that will reduce foam in the rumen.
  4. Seriously affected animals (having difficulty breathing, open mouth, tongue out) need immediate assistance to either reduce the foam or remove it. As a last resort, an incision can be made in the upper left flank to allow the foam to escape. While this approach may save the bloated animal it is essential to call your vet immediately to repair the wound and administer antibiotics to counter infection.

Risk factors

Overconsumption of young, rapidly growing legumes, clover or lucerne pastures


Only introduce animals when their appetite has been partially satisfied with safe pastures, hay or silage. Limit grazing time and observe cattle closely to assess the risk and act quickly if animals start to show signs of bloat.

Administer anti-foaming chemicals:

  • detergents such as the teric group of chemicals
  • anti-foaming agents (bloat oils) such as paraffin oil and tallow
  • rumen modifiers such as monensin

Most anti-foaming chemicals are only effective for a relatively short time. The major challenge is to ensure that animals have a continual supply of the chemical in their rumen. Systems for maintaining a safe level of chemical in the rumen include:

  • drench twice a day
  • spray pastures with oil
  • mix the medication with feeds that delivered in the bail during milking
  • flank application of bloat oil - some animals do not lick the oil and are not protected
  • add detergents to drinking troughs
  • bloat blocks – limited success because not all animals will lick the blocks
  • bloat capsules - designed to stay in the rumen and slowly release monensin for ~ 3 months

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