Bloat in cattle is a condition caused by the excessive buildup of gas within the rumen, the largest compartment of a cow’s stomach. This accumulation occurs when the normal process of gas elimination, known as eructation or belching, is interrupted. The trapped gas causes the rumen to expand, exerting pressure on surrounding organs, which can interfere with breathing and blood flow. This condition can escalate rapidly, becoming life-threatening if not addressed promptly.
Recognizing the Signs of a Bloated Cow
The most prominent sign of bloat is a distension of the animal’s left flank. This swelling occurs because the rumen is located on the left side of the abdomen. As gas accumulates, this area will appear tight and drum-like. The severity of the swelling can range from a slight bulge in mild cases to a massive protrusion in severe instances.
A bloated cow will also show clear signs of distress and pain. They will often exhibit restlessness, repeatedly lying down and getting back up. They may kick at their belly, stomp their feet, or vocalize with grunts or bellows. As the distended rumen presses against the diaphragm, the cow will experience difficulty breathing, leading to rapid, shallow breaths and an open mouth with a protruding tongue.
Other observable signs include excessive salivation, a reluctance to move, and straining as if to urinate or defecate. In advanced stages, the pressure on vital organs can become so great that the animal may stagger or collapse.
Understanding the Causes of Bloat in Cattle
There are two primary classifications of bloat in cattle: frothy bloat and free-gas bloat. Frothy bloat, also called primary ruminal tympany, is the more common form and occurs when fermentation gases get trapped in a stable foam within the rumen. This foam prevents the small gas bubbles from merging and being expelled through belching.
The primary cause of frothy bloat is dietary. It happens when cattle graze on lush, rapidly growing legume pastures, such as those rich in alfalfa and clover. These plants contain natural foaming agents that contribute to the creation of the stable foam. Similarly, high-grain diets, common in feedlot settings, can lead to frothy bloat due to rapid fermentation of finely ground grains.
Free-gas bloat is a result of a physical obstruction or a functional issue that prevents the cow from belching. The gas separates from the rumen contents but cannot escape. A common cause is an esophageal obstruction, where an object like a potato, apple, or beet becomes lodged in the gullet. Other causes can include nerve damage from conditions like pneumonia that impair rumen motility or issues like milk fever that prevent the animal from burping.
Addressing a Bloated Cow and When to Call a Vet
Bloat in cattle is a veterinary emergency. If you suspect an animal is bloated, contacting a veterinarian should be the first step. While waiting for professional help to arrive, there are a few safe actions that can be taken.
If it can be done safely, remove the entire herd from the suspected source of the bloat, such as a high-risk pasture. For mildly affected animals, encouraging slow walking may help break down the foam and promote the release of gas. It is important not to stress the animal, as this can worsen the situation.
For free-gas bloat, a common procedure is to pass a stomach tube down the esophagus to release the trapped gas. If the cause is frothy bloat, the tube can be used to deliver anti-foaming agents, such as mineral oil or poloxalene, directly into the rumen to break down the foam. In life-threatening situations where the pressure is extreme, the vet may perform an emergency procedure using a trocar and cannula to puncture the rumen wall and release the gas directly.
Strategies for Bloat Prevention
Effective management practices are key to prevention. For pasture-related frothy bloat, prevention focuses on careful grazing strategies. Avoid turning hungry cattle onto lush legume pastures. Providing access to dry hay before turnout can help fill the rumen and reduce the intake of high-risk forage.
Using mixed grass-legume pastures with a legume content of less than 40% lowers the risk. Another strategy is strip grazing, which limits access to small sections of pasture at a time. The use of anti-bloat agents, such as poloxalene, is administered through bloat blocks, licks, or added to water troughs.
In feedlot operations, prevention involves a gradual adaptation period. Slowly increasing the amount of grain in the diet over several weeks allows the rumen’s microbial population to adjust. Ensuring that the diet contains adequate roughage, 10-15%, helps maintain normal rumen function. To prevent free-gas bloat, chop large items like potatoes or apples into smaller pieces to avoid an obstruction.