Bloat is a condition that occurs when an excess amount of fermentation gasses become trapped within the rumen of an animal. This condition can occur in any ruminant species including beef and dairy cattle, sheep and goats. Bloat can occur very rapidly and can quickly become a life-threatening condition if not treated. There can be many different causes for bloat and the appropriate treatment is based on determining the underlying cause.
Bloat can be differentiated into two categories; free gas bloat and frothy bloat. Free gas bloat is just that, an accumulation of free gas within the rumen due to a failure of the animal to eructate or burp the gas out. Cattle are capable of eructating enough to compensate for maximal gas production within the rumen, so the problem is never too much gas production, but instead, is always a failure in eructation. Free gas bloat can result from an obstruction within the esophagus, damage to nerves innervating the rumen and diseases such as tetanus, rumen acidosis and milk fever. Frothy bloat occurs when the excess gas within the rumen is contained in a foam. The animal cannot eructate foam and, in turn, the gas builds up causing bloat.
Frothy bloat is often associated with diet. Several forages are known to increase the risk of frothy bloat such as alfalfa, clover, winter wheat and ryegrass. Excess grain can also lead to frothy bloat, in particular, those rations with very small particle size.
If a calf or small ruminant is bloating, the earliest clinical signs include decreased appetite and depression. Eventually, the animal begins showing signs of abdominal discomfort and distention becomes evident, and is most notable on the left side. If the condition is left untreated the rumen can distend to the point that severe pressure is placed on the diaphragm and the animal becomes unable to breathe and eventually dies. This series of events can occur in less than one hour in very acute cases.
If an animal is found bloated and is having difficulty breathing then emergency treatment is warranted. A trochar can be placed in the side of the animal or a stab incision made directly into the rumen from the side of the animal’s abdomen to quickly relieve the gas build up. For non-emergency cases a stomach tube is passed to allow escape of the accumulated gases. In the case of frothy bloat a surfactant such as poloxalene (Thera-bloat) or mineral oil can be administered via stomach tube to eliminate the foam and allow the animal to eructate. In each case the predisposing cause should also be considered, whether that be a disease process or a problem with the ration.
Allowing animals to acclimate to high risk forages and grain rations will help in preventing cases of bloat. Additionally, bloat prevention products are available for use as feed and water additives and supplements. Ionophores such as rumensin have also been shown to reduce the number of cases of bloat in cattle.
Darren Loula, DVM, is a large animal veterinarian at Fair Grove Vet Service in Fair Grove, Mo.
