Kerry Rood, DVM

Kerry Rood, DVM

Acute tympanites, also known as bloat, is a non-infectious disease common among ruminant animals. Bloat can become apparent when carbon dioxide and methane gases build up within a cow’s stomachs, leading to abdominal swelling. Bloat can be caused by diet or by some type of throat obstruction.

Swelling will first become apparent in the triangular area located between the last rib and the point of the flank on a cow’s left side, also known as the paralumbar fossa. If the problem persists, swelling will appear on the animal’s right side, too. The degree of swelling may not always indicate the amount of distress the animal is experiencing.

Other signs include an arched back with rear feet stretched far back, kicking at the abdomen, staggering gait, vomiting, frequent urination and defecation, labored breathing with nostrils dilated, tongue extended and eventual collapse, followed by death.

Bloat can be categorized into three main types: diet-related free gas, obstructive free gas and frothy.

Diet-related free gas bloat usually occurs when an animal eats too much concentrate feed. This accelerates the fermentation process within the rumen. Rumen bacteria overproduce volatile fatty acids which cause an increase in lactic acid and a lowering of rumen pH. This acidic environment inhibits normal rumen function and allows gas buildup and bloat.

Diet-related free gas bloat can be prevented by making feed particles larger and coarser, implementing a consistent feeding regimen and supplying rumen antibiotics to regulate the rumen bacteria (e.g., Rumensin).

Treatment options for diet-related free gas bloat can include the passage of a tube down the esophagus to the rumen to relieve the gas pressure. Sodium bicarbonate (baking soda) diluted in water can be administered through the tube if acidosis is believed to be the cause of the bloat.

Obstructive free gas bloat is caused by physical obstructions in a cow’s esophagus. This traps gas in the rumen by preventing the cow from belching. Blockages can occur when the animal swallows a large object — such as whole potatoes, beets, hedge-row gourds or whole fruit — that becomes lodged in the esophagus.

Obstructive bloat may also be relieved through the use of an esophageal tube, but caution is advised to prevent damage to the esophagus.

Frothy bloat occurs in animals grazing lush legume pastures. The viscous, slimy mass produced in the ruminant’s stomach can trap gases and prevent belching. Legumes are high in protein and are highly digestible, which leads to increased incidence of frothy bloat.

Frothy bloat can be prevented by limiting forage of certain legume species, growing bloat-free legumes with grass, feeding a dried grass hay before turning out to pasture and turning animals out after the dew is off.

Frothy bloat treatment can include administering surfactants such as Poloxalene (e.g. Bloat Guard) and vegetable or mineral oil to help break down the foam. If an animal is in severe respiratory distress, a rumen trocar and cannula can be used.

If an animal collapses, the interior of the rumen can be exposed by making an incision about 15 cm [6 inches] long in the left paralumbar fossa area. If possible, this procedure should be performed by a veterinarian or at least with a veterinarian’s supervision. This should be a last resort option, as it can cause the rumen contents to leak into the abdomen cavity, risking peritonitis or infection of the abdomen lining.

As with most diseases, the best treatment for bloat is prevention. Consult a veterinarian if your livestock display signs of bloat or for information about forage and grazing management practices to prevent bloat.

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