The old cow had been down for a while. She looked uncomfortable and her belly was as tight as a drum. The vet was called, and on arrival, the good doctor passed a tube through the cow’s mouth to her rumen. When the hose made it to its mark, the eruption of gas was enough to knock out three horseflies and cause the neighbors to blame the smell on the dog.
With the pressure off her belly, the bovine was ready to go, yet there is still the question of why.
Bloat can occur in two forms. In this case, free-gas bloat afflicted the patient. Free-gas bloat is caused by a failure of the cow to eructate, or burp. Gas is produced during normal digestion, and they burp with their cud to alleviate the built-up gas. Free-gas bloat can be caused by a blockage of the esophagus (horse apple, onion and sugar beet in Northern climes) or inability to burp, such as tetanus, milk fever or grass tetany.
In the spring and fall, frothy bloat commonly occurs. The breakdown of lush forages like clover and alfalfa increase the viscosity of the fluid in the rumen, which causes the liquid to form small bubbles that prevent the gas from escaping the rumen.
The most obvious sign of bloat is a distended left side of the abdomen. The animal may appear to be in pain. In some cases, death can occur quickly and may be the first sign that is seen. While free-gas bloat will usually affect one animal, it is possible for frothy bloat to be seen in multiple animals in a herd at the same time.
Treatment of free-gas bloat may simply involve passing a tube or puncturing the rumen with a trocar to remove the gas, then treating the underlying cause. Frothy bloat needs to be medicated with substances that will break down the froth. If multiple animals are affected, it is best to pull the herd from the pasture and offer hay while treating the affected cattle.
Prevention is the best approach to bloat. Manage high-risk pastures by introducing cattle to them slowly, making plenty of hay available to increase their available fiber. Don’t turn them out on the pasture while it is wet. There may be benefit to making bloat guard blocks that contain medications like poloxalene to prevent frothy bloat. Maintaining a proper diet through the variation of pasture conditions will help avert the risk of bloat.