There has been an increase in the number of reports of bloat
from NADIS vets this month. Bloat is most commonly seen in spring
and autumn, when grass growth is at its peak. It is one of the most
common causes of death in adult cattle at grass
What is bloat?
Bloat is simply the build up of gas in the rumen. This gas is
produced as part of the normal process of digestion, and is
normally lost by belching (eructation). Bloat occurs when this loss
of gas is prevented. There are two sorts of bloat. The least common
type is gassy bloat, which occurs when the gullet is obstructed
(often by foreign objects such as potatoes) or when the animal
can't burp (such as with milk fever or tetanus). The second type of
bloat is frothy bloat, which happens as the result of a stable foam
developing on top of the rumen liquid, which blocks the release of
the gas. This is by far the most common form of bloat, and unlike
gassy bloat, it is highly seasonal with peaks in the spring and
autumn. This is because the foam is formed by breakdown
products from rapidly growing forages (particularly legumes such as
clover and alfalfa). These increase the viscosity (stickiness) of
the rumen fluid and prevent the small bubbles of gas formed by
rumen fermentation from coming together to form free gas that can
be belched off
- Distended left abdomen is the most obvious sign
- Usually associated with pain, discomfort, and bellowing.
- Death can occur within 15 minutes after the development of
- Gaseous bloat is usually seen in one or two animals. Frothy
bloat can affect up to 25% of cases
- In some cases sudden death may be the first sign seen by the
stockman, although in such cases it is likely that there will
be other cattle with bloat that are still alive
- On the clinical signs described above
- History of access to lush pasture
- Passing a stomach tube will distinguish between gassy and
frothy bloat. If it's gassy bloat a stomach tube passed into the
rumen will allow the gas build-up to escape through the tube. No
such gas is seen in frothy bloat.
- Passing a stomach tube is the best treatment for gassy bloat.
Once the gas has been released, the cause of the obstruction should
be looked for.
- In a few cases a trochar and cannula punched through the side
into the rumen will relieve gassy bloat when a stomach tube has not
worked. But such cases are rare, and as the trochar provides a
tremendous opportunity for introduction of infection, it should
only be used as a last resort.
- For frothy bloat, antifoaming agents that disperse the foam
should be given by stomach tube. Old-fashioned remedies such as
linseed oil and turpentine are effective but newer treatments such
as dimethicone or polaxolene are easier to give as the effective
dose is much smaller.
- If an outbreak of frothy bloat occurs all cattle on that
pasture should be removed immediately and put onto a high fibre
diet (hay or straw), and any cows showing bloating signs treated
with an anti-foaming agent. The pasture should not be grazed for at
least ten days.
It is much more effective to prevent bloat than treat affected
animals. Management and planning can significantly reduce the
number of cases. To prevent frothy bloat:
- If possible avoid using high-risk pastures at high-risk times.
Pastures with a history of bloat problems or with a high clover
content should not be used for cows soon after turnout.
- Stagger turnout with buffer feeding as this will allow the
rumen to adapt to the new diet. In particular try and keep up fibre
intakes at risk periods.
- If you have to use high-risk pastures, introduce the cattle to
them slowly. In some cases restricting access to as little as ten
minutes per day at the start may be necessary to prevent
- Avoid starting to graze high-risk pastures when they are
- Administer anti-foaming agents daily if bloat is a severe
problem. If this is the case and you can strip graze then spraying
antifoaming oils (emulsified with water) onto the grass can
significantly reduce labour costs.
- Remove high-risk animals. Some animals have recurrent bloat
despite prevention and treatment.