An Udder Disaster: Mastitis in Cattle

Mastitis is one of the largest health challenges cattle face. Mastitis is inflammation in the mammary gland caused by trauma or infection, leading to abnormal milk and decreased production. Common bacterial causes of mastitis include staphylococcus aureus, streptococcus species, mycoplasma species, and E. coli. Many other environmental pathogens cause disease less frequently. Mastitis can occur at any point in lactation but is more common during high-stress times such as post-calving. Common symptoms that producers may observe in cows with mastitis include redness or heat of the udder, flaky or clotted milk, and color change of the milk, usually yellow or red-tinged. Systemic symptoms can occur in more severe cases, including fever, going off-feed, and shock and death in very severe cases.

The three general classes of mastitis are subclinical, clinical, and chronic. Sub-clinical mastitis can also be called asymptomatic, as there are no visual changes to the milk or udder. Usually, this can only be diagnosed by looking at a cow’s somatic cell count or performing a California mastitis test. An increased somatic cell count above 200,000 cells per ml indicates a high likelihood of infection. A California mastitis test uses a reagent mixed with cow’s milk to produce a clotting-like reaction in cases with a high somatic cell count. This can be performed cow-side for immediate results.

Mastitis is classified as clinical when there are visible changes to the milk or udder with or without systemic involvement. The producer or farm workers usually quickly diagnose clinical mastitis upon observation of a cow’s udder or a few squirts of milk. It is easiest to see changes in the milk on a dark surface, such as a black paddle or rubber glove. Farm workers often observe clotted, flaky, or stringy milk when stripping out a cow before milking. Beef cattle, whose milk is not observed daily, may need to be detained in a chute to palpate and strip out her udder to see signs of clinical mastitis. One more easily observable symptom in beef cows is a mother cow kicking her calf away from her udder because it is painful to her if the calf sucks.

Chronic mastitis can start as either clinical or subclinical, and it is classified as chronic if it does not resolve in 2 months. Usually, this is most easily seen on a dairy farm with DHIA testing performed, as the DHIA testing can show cows with two test days with increased somatic cell counts. Chronic infections can often last for an entire lactation or the cow’s entire life. It may be wise to cull these chronic cows as they consistently contribute to an increase in bulk tank somatic cell count. On a beef operation, these chronic cows may not be able to support their calf and may have premature dry off of one or multiple teats.

A consultation with your veterinarian is the first step in treating mastitis. Your veterinarian will need to determine the cause of the infection by taking a small milk sample and inoculating agar plates to see what bacteria grow. If your veterinarian does not have an in-house lab, they may send the milk sample to a university lab. Once the bacteria type is determined, the best treatment decision can be made. The most common treatment is an intermammary antibiotic, such as ceftiofur, cephapirin, pirlimycin, or amoxicillin. Your veterinarian can work with you to determine the antibiotic based on the isolated bacteria. Occasionally, no bacteria are isolated from a milk sample, and those cases do not need antibiotics. Some mastitis cases need more supportive therapy, such as an anti-inflammatory drug, and very severe cases might need IV fluids or an oral drench. Other diseases, such as ketosis and metritis, can negatively impact the cow’s ability to clear a mastitis event, making it essential to treat those concurrently. In a beef animal, separating the calf from the dam may be necessary if she is treated to keep the calf from removing the antibiotic infusion from the udder.

Many best practices can be implemented to prevent mastitis. On a dairy, good udder handling during milking is crucial in preventing mastitis. Using clean gloves and towels when prepping the cow can help limit the spread of mastitis-causing bacteria. Also, appropriate pre and post-dip should be used. If possible, cows known to have mastitis should be separated from those that don’t and should be milked at the end of a shift or in a separate parlor. This allows the milking units to be thoroughly cleaned before being used on non-infected cows. Teat end health is also important in preventing mastitis. Milking units should be attached at the correct time after stimulation and promptly removed when the cow is finished milking. Routine evaluation of milking equipment for appropriate vacuum levels can also help maintain teat end health. Some vaccines can help with some types of mastitis, such as E. coli
Cleanliness of the pens is another factor in the prevention of mastitis. The bedding should be dry, and alleyways should be regularly scraped to remove manure. Inorganic bedding, such as sand, supports less bacterial growth than organic bedding, like sawdust or dried manure solids.

Keeping the environment clean and dry in a beef operation is the most critical step in preventing mastitis. Due to the high volume of animals in a small space, the calving pen is one of the most significant sources of mastitis pathogens. Cleaning the calving pen regularly and frequently providing fresh bedding will lessen the pathogen load. Reducing access to standing water can help prevent infection. Early detection in beef cows can also help the producer separate these infected cows to limit the spread between cows.

If you suspect a mastitis issue, call your veterinarian early. Early intervention allows for more successful treatment and less production loss. Some cases may never reach a favorable outcome, so working with your veterinarian to make a protocol for culling cows with repeat infections or chronically high somatic cell counts is wise. Implementing prevention practices and promptly treating infected animals leads to a better outcome for farms dealing with this costly disease.