There are two kinds of “lump jaw” in cattle — soft-tissue abscesses arising from wounds in the mouth, and bone infections (bony lump jaw).

Soft-tissue abscesses often result from foreign objects embedded in the mouth, such as sharp grass seeds, which are easily treated by lancing, draining and flushing. A bone infection, however, takes diligent effort to eradicate, says Geof Smith, a North Carolina State University ruminant specialist.

Smith says bony lumps are caused by Actinomyces bovis. The technical term for this bacterial infection is Actinomycosis.

“Since the Actinomyces bovis bacteria live in the soil, we think some kind of penetrating wound in the mouth is needed for it to enter the bone. It isn't transmissible between animals,” Smith explains. And it usually involves a deeper wound than what typically causes a soft-tissue abscess.

A mouth wound may be caused by wire or other sharp material baled up in hay, by chewing on sharp sticks (as when browsing on trees) or eating abrasive feed.

“In instances of multiple cases on one farm, bony lump jaw is usually due to coarse feed (poor quality or stemmy hay) or sticks in the feed. Typically, however, it's sporadic and you only see a case every 4-5 years on a farm,” Smith says.

Some people speculate bacteria enters via the dental sockets when young animals shed baby teeth, which may be why the condition is often seen in two- and three-year-olds. Smith says he's not aware of a reported case in an animal under two years old.

Smith points out that a penetrating wound into the bone needn't come from inside the mouth, however. The animal may run into something sharp and develop the infection. Bony lumps have been seen on the front of the face, as well.


The clinical signs are a painless facial enlargement, usually near the area of the central molars, which appears after infection gets into the bone. Some lumps develop within a few weeks; others over several months.

A general thickening on the lower edge of the lower jawbone may go unnoticed until it's quite large. More commonly, a more noticeable protrusion on the side of the bone occurs. Compared with a soft-tissue abscess that can be moved by hand pressure, the bony swelling is very hard and immobile, Smith says.

“If we want to confirm a diagnosis, we collect some of the oozing fluid to culture. If it's not open, we'll aspirate the bony lump with a needle to acquire a sample. If it's a valuable animal, we may take a radiograph of the head to see how extensive the bone involvement is,” he says.

Unless treated, the bony infection — and the lump — will continue to grow, and may eventually break through the skin. Initially there's no effect on the animal's general health, but the area may become painful and interfere with chewing in later stages.


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“It also may cause the teeth to loosen. Generally it affects the cheek teeth, usually in the lower jaw, but occasionally the top teeth,” Smith explains.

In long-standing cases, the affected jawbone may become misaligned, with the infection spreading to soft tissues, as well as the muscles and lining of the throat. The animal may have trouble eating and become so thin that destruction is necessary. Extensive swelling can also interfere with breathing.

Since the condition progresses slowly, however, there is time to treat it before the animal's health is compromised. Treatment should begin when the bone enlargement is first noticed.