F.C. 20.1 Apr, 1993
What is bloat?
Bloat is a digestive disorder characterized by an accumulation of gas in the
first two compartments of a ruminant's stomach (the rumen and reticulum).
Production of gas (primarily carbon dioxide and methane) is a normal result of
fermentation processes. The gas is usually discharged by belching (erutication)
but, if the animal is unable to remove the excess gas, pressure builds up in
the rumen-reticulum exerting pressure on the diaphragm which prevents the
animal from inhaling, and bloat occurs. The most common type of bloat is frothy
bloat where gas builds up in a foam or froth above the rumen contents and the
normal belching is inhibited.
Observable bloat can occur after as little as 15 minutes of grazing. Often
the animal bloats only mildly and stops eating. The discomfort is eventually
relieved. In more severe bloat, the animal's rumen is distended by ballooning
of the rumen, it urinates and defecates frequently, bellows and staggers.
Death, due to restricted breathing and heart failure follows unless action is
When is it likely to occur?
Bloat can occur on any forage that is low in fiber and high in protein but
is most common on immature legume pastures. Bloat has been observed on alfalfa,
white clover, and red clover pastures but is rare on trefoil sainfoin and vetch
pastures. It usually occurs when cattle or sheep are first turned onto legume
pastures. It seldom occurs on grasses, (or pastures with at least 50% grass),
coarser pastures, or hay. Bloat usually follows a heavy feeding or grazing
period. Animals that are hungry or greedy feeders are most susceptible. Frost,
dew or rain on the field often increase the likelihood of bloat. Bloat incidence
is likely to be increased during periods of rapid plant growth in the spring or
following a summer rain.
Thus, most bloat occurs:
- when cattle are first turned
onto pastures in the spring
- when cattle are moved to new
pastures if the previous pasture was grazed too short so that cattle are
- in late summer, during
periods of rapid plant growth after rain following a period of drought.
How do I reduce the occurrence of bloat?
- Begin grazing in the spring
on pastures that are grass or grass-legume (at least 50% grass) mixtures.
This will allow the animal time to adjust to the pasture.
- Make sure that the animal is
full when first put onto pasture in the spring. This reduces the intake of
the fresh pasture until the rumen has had time to adjust to the new
- Do not start animals grazing
when the forage is wet from dew or rain.
- Start animals on legume
pastures gradually. For example, leave cattle on pasture 1 hour the first
day and gradually increase grazing time to 4 hours by the third day and
day-long grazing by day 5.
- Be sure that fiber is
maintained in the animal ration during initial grazing periods. Feed some
dry hay or corn silage to grazing animals prior to turning them out to
- Check animals for bloat
carefully every 2 hours when beginning grazing.
- When rotating cattle or sheep
among pastures, be sure that animals are moved fast enough so that they
are not excessively hungry when going onto fresh pastures.
- Animals with supplemental
feed will be less likely to bloat. For example, a dairy cow, where 40 to
50% of the intake is pasture will be less likely to bloat than beef
cattle, dairy heifers, and sheep, where pasture comprises 100% of the
- Where bloat has been a
problem, consider seeding using birdsfoot trefoil as the legume because it
- Consider using Bloat Guard®
(Poloxalene) during periods where bloat is likely. Poloxolene can be mixed
with grain supplement or drinking water, drenched, or fed as a pasture
block. Effectiveness of this product depends an daily intake. Thus mixing
with a daily supplement is more effective than feeding in blocks on
- Some animals are chronic
bloaters. If a particular animal frequently shows signs of bloat, it may
be best to remove that animal from the herd.
What do I do if bloat occurs?
When bloat is observed, immediately remove all animals from pasture and
offer dry hay. This will reduce the bloat problem in all animals that will eat.
Causing bloated animals to walk is also helpful. Bloat can cause death in as little
as 1 hour so it is important to be prepared to render emergency treatment.
Materials and directions for use can be obtained from the local veterinarian.
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