| Livestock Disease Summaries | नेपाली भाषा |
Rumen Bloat
Bloat is a common problem in cattle and buffalo, and sometimes is also seen in goats and sheep. Huge amounts of gas are constantly being produced in the rumen by microbial fermentation. That gas is normally eliminated by belching, which ruminants spend a lot of time doing. Anything that interferes with the animal’s ability to eliminate ruminal gas will quickly cause a major problem known as bloat. Animals with bloat do not explode, but when the rumen becomes distended with gas, they have great difficulty breathing and can rapidly die. Sudden death is a frequent result of bloat and this condition needs to be considered a medical emergency.
Two types of bloat are observed, corresponding to different problems that prevent normal elimination of gas in the rumen:
1. Frothy bloat results when fermentation gases are trapped in a stable, persistent foam which is not readily eructated. As quantities of this foam build up, the rumen becomes progressively distended and bloat occurs. This type of bloat occurs most commonly in two settings:
- Animals on pasture, particularly those containing alfalfa or clover (pasture bloat). These legumes are rapidly digested in the rumen, which seems to result in a high concentration of fine particles that trap gas bubbles. Additionally, some of the proteins from such plants may serve as foaming agents.
- Animals feed high levels of grain, especially when it is finely ground. Again, rapid digestion and an abundance of small particles appear to trap gas in bubbles. Some species of bacteria that are abundant in animals on high concentrate rations produce an type of slime that results in formation of a stable foam.
- Bloat on pasture is frequently associated with "interrupted feeding" - animals that are taken off pasture, then put back on, or turned out on pasture for the first time.
2. Free gas bloat occurs when the animal is unable to eructate free gas in the rumen. The cause of this problem is often not discovered, but conditions that partially obstruct the esophagus (foreign bodies, abscesses, tumors) or interfere with rumen motility can be involved.
Regardless of whether bloat is of the frothy or free gas type, distention of the rumen compresses the thorax interferes with lung function. The cause of death is usually respiratory failure.
Clinical Signs
Bloat is very easy to diagnose: the animal has a very distended abdomen, especially on its left side, as seen in the photos below. As gas continues to accumulate, the entire abdomen becomes distended.
In addition to abdominal distension, other signs of bloat often include:
- Reluctance to move and lack of feed consumption
- Signs of distress: anxiety and vocalization
- Respiratory distress: rapid breathing, neck extended with protruding tongue
- Staggering and recumbancy: once an animal with bloat is recumbent, death occurs rapidly.
Ruminants that die of any cause usually develop a distended abdomen because gas production in the rumen will continue after death. If the animal did die from bloat, a simple necropsy will reveal what is called a “bloat line” in the esophagus: the color of the esophagus in the neck will be reddened but as the esophagus enters the thorax, it becomes distinctly pale due to the pressure on the chest cavity from the distended rumen.
Treatment and Control
Bloat is a life-threatening condition and must be relieved very rapidly. There are several treatments that can be applied to bloated animals:
- Attempt to release the gas by passing a large-bore stomach tube; it may be necessary to reposition the tube several times. This procedure is useful in free gas bloat but often does not work for frothy bloat.
- Antifoaming medications such as vegetable oil, mineral oil or a commercial anti-bloat product such as polaxalene (a surfactant) or alcohol ethoxylate (a detergent) can be delivered directly into the rumen through the stomach tube; the animal should then be closely observed to insure that the treatment is effective and the animal begins to belch gas. The dose of vegetable oil or mineral oil for a cow is 250-500 ml.
- If use of a stomach tube or antifoaming agents does not relieve the bloat rapidly, a rumen trocar is often an effective treatment. This device is inserted directly into the rumen through the left paralumbar fossa and can be left in place for several days if it is the type that can be screwed into the rumen to secure it to the overlying skin. The video below shows how to insert a corkscrew type of rumen trocar.
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