Now, the animals have
been stepped-up to the high-grain diets and they
are close to their maximum intake capacity. We
have already overcome the plague that respiratory
diseases are in those newly arrived. Also the
stress of the first days on feed, diarrhea, lack
of appetite and hopefully deaths associated with
newly arrived cattle problems are past history.
Then we are ready to take advantage of the already
transitioned digestive tract environment (rumen
bugs are adapted to the presence of grain and digest
it efficiently) and we are ready to start putting
weight on these animals… however, one more
hurdle needs to be jumped: feedlot bloat.
What is feedlot bloat?
In simple terms, feedlot bloat can be defined
as a disruption in the rumen function that promotes
the formation of stable foam impairing the normal
elimination of the gas produced during the digestive
processes. The consequences of feedlot bloat can
range from a minor reduction in feed intake to
sudden death by impaired respiration resulting
from the pressure from the expanded rumen on lungs
Even though the obvious
impact of feedlot bloat is an increased mortality,
cattle death is not the only economic loss. Perhaps
the greatest impact of bloat on feedlots’ profitability
is due to reduction in animal performance (reduced
intakes), increased culling due metabolic disorders
and increased treatment costs of bloaters.
What causes feedlot bloat?
Feedlot bloat can be caused by several factors
and the interaction of them. Typically feedlot
bloat is associated with the intake of large amounts
of grain, specially those types of grain that ferment
rapidly in the rumen such as wheat or barley. Even
though the presence of large amounts of grain in
the diets is a triggering factor, management and
animal factors contribute to the development of
bloaters. When the grains enter the rumen they
are fermented by the rumen microbes producing large
amounts of gas. Normally those gases are released
by waves of rumen contractions followed by eructation,
but under certain conditions such as: excessive
amounts of gas produced, reduced rumen contractions,
obstructions in the upper gastro intestinal tract,
etc, bloat can occur.
Contribution from the rumen microbes cannot be
ignored. The viscosity of the rumen fluid can be
increased by the formation of slime by the rumen
bugs, which will contribute to the formation of
stable froth. Proliferation of certain types of
microbes in the rumen triggers the produce of slime,
and those types of bacteria are usually the ones
that grow fastest under high-grain diets. This
serves as another example (besides the excess production
of gases) of how high-grain diets can prompt the
incidence of bloaters.
Types of feedlot bloat
Bloat can be classified in two types: free-gas
bloat and frothy bloat. Free gas bloat is of rapid
onset and often lethal. The animals presenting
free-gas bloat usually die suddenly as a result
of an obstruction in the esophagus impairing the
elimination of gases. These obstructions can be
caused by undigested feed particles or partially
chewed feeds that can block the esophagus. Free-gas
bloat can also be caused by chronic pneumonia or
hardware disease as they may affect rumen motility
by damaging key nerves involved in those mechanisms.
Free-gas bloat can be relieved by removing the
obstruction or making a rumen fistula (minor surgery
creating a hole from the rumen to the outside)
allowing gas escape. Free-gas bloat does not happen
as frequently, but its often lethal consequences
sure gives them more press than frothy bloat.
Frothy bloat is the most common type of bloat
and rarely leads to death. Animals with frothy
bloat present a stable mix (bubbles) of gas and
liquid at the top of the rumen that traps feed
particles and prevents gas release. In frothy bloat
caused by pastures, legumes such as alfalfa or
red clover are responsible for the formation of
stable foam. In the case of feedlot frothy bloat
the responsible agents for the formation of foam
are the rumen microbes.
Even though feedlot bloat has been associated
with acidosis, resulting from high-grain diets
and intake variations, both types of metabolic
disorders can occur independently from each other.
How can we prevent it?
The causes are complex and often hard to predict.
The use of grains has been indicated as the factor
always associated with bloat; however, reducing
the amount of grain to be fed is usually not an
option, as animal performance would be reduced.
Fed management strategies are probably the most
common and cost-effective tools to prevent feedlot
Replacing the use of highly fermentable grains
in the rumen such as wheat or barley in finishing
rations for other sources such as corn is a viable
alternative. Also the processing method will play
a key role in bloat prevention as may limit the
amount of starch that will be degraded in the rumen.
Whatever is not digested in the rumen does not
mean that will be wasted. The small intestine still
will use part of that starch without risk of bloat.
In general, the smaller is the particle size of
the grain, the greater the chances of developing
bloat, as more surface will be exposed to the microbes
Feed additives such as ionophores and bloat preventives
have been widely used. Ionophores such as monensin
and salinomycin prevent bloat by inhibiting specific
types of microbes or reducing feed intake. Bloat
preventives such as poloxalene are most commonly
used in pasture bloat and are low-foam detergents
that reduce foam stability in the rumen.
In summary, bloat is a metabolic disorder that
can harm the economic success of your beef operation;
however, a set of tools, management practices and
good amount of information are available to prevent
or minimize feedlot bloat incidence and enhance