Abscesses in cows are localised, pus-filled infections that can develop due to injury or infection, or bacteria entering the body through open wounds or compromised skin.  An abscess is a defence mechanism that helps prevent the spread of infection to other parts of the body. Abscesses have a wall, or capsule, that is formed by adjacent healthy cells in an attempt to keep the pus from infecting neighbouring structures. However, this capsule will also prevent immune cells and antibiotics from reaching the bacteria in the abscess.

Abscesses usually appear as firm, swollen lumps, often found around the neck, shoulder, flank or the back of the legs, but can occur on almost any part of the body. They may start small but can grow rapidly. It is not uncommon to see an abscess the size of a football, containing upwards of five litres of pus.

Many cows with abscesses appear otherwise healthy, but, if left untreated, an abscess is likely to cause discomfort, disrupt milk production, and even lead to systemic infection.

The most important aspect of treatment involves lancing and draining the abscess, ideally by a veterinarian. An X-shaped hole is recommended to prevent the wound sealing shut too early, which could allow the abscess to fill up again. Where possible, the hole should be located to enable it to drain freely via gravity, and it should be big enough to insert a finger into the abscess to allow exploration for foreign bodies (sticks, bits of wire, pieces of bone, etc) or pieces of firm pus or necrotic tissue that can block the hole and impede drainage.

The abscess should be thoroughly flushed, ideally with dilute iodine or chlorhexidine, but if drainage of the abscess is good, tap water will be ok.

I would strongly recommend administering local anaesthetic before lancing an abscess, as it is necessary to make more than one cut through thick cow skin, sometimes also through muscle, as well as through the abscess capsule. Although the area is under pressure from the abscess, this will still be a painful procedure for the cow. An anti-inflammatory, such as Metacam or Ketomax, may also be given to provide further pain relief and help reduce inflammation and swelling at the abscess site. Antibiotics are usually not given due to the abscess capsule.

The abscess should continue to be flushed out for a further two to five days, and during this time, it is good practice to continue to explore the hole with a gloved finger to search for any objects that could contribute to the infection, or that may block the drainage hole.

Preventing abscesses can be difficult, but if there is an outbreak of abscesses with a common location, consider investigating broken gates and rails, faulty equipment, and injection hygiene and technique.

Regularly inspecting cows for signs of injury or infection is crucial, as early detection leads to easier treatment.