What is Mastitis in Dairy Cows and How is it Diagnosed?

Mastitis is among the most common and economically significant diseases affecting dairy cows. It is an inflammatory condition of the mammary gland, primarily caused by bacterial infection, which can lead to decreased milk production, reduced milk quality, and increased veterinary costs. Dairy farmers must be vigilant in detecting, diagnosing, and managing mastitis to maintain herd health and optimise milk production.

Types of Mastitis

Mastitis presents in two main forms:

1. Clinical Mastitis: This form is easy to detect as it presents with obvious physical symptoms. Affected cows may show signs such as a swollen or reddened udder, heat, and pain. The milk may appear abnormal, showing clots, blood, or a watery consistency. A cow suffering from clinical mastitis may also exhibit general signs of illness, such as a reduction in feed intake or an increase in body temperature.
2. Subclinical Mastitis: Unlike clinical mastitis, subclinical cases are harder to detect because the cow may not show visible symptoms. However, this form can be just as damaging, as it often goes unnoticed, allowing the infection to spread within the herd and affecting milk production over time. A key indicator of subclinical mastitis is an elevated somatic cell count (SCC) in the milk, a measure of white blood cells that increase in response to infection.

Causes of Mastitis

Mastitis is generally caused by bacterial pathogens entering the udder through the teat canal. The most common bacteria include Staphylococcus aureus, Streptococcus uberis, and Escherichia coli. These bacteria can be spread through poor milking practices, contaminated bedding, or exposure to an unsanitary environment.

Environmental and management factors also significantly influence the development of mastitis. Inadequate milking hygiene, improper bedding conditions, stress, and nutritional deficiencies can all predispose cows to infection.

Diagnosing Mastitis

Early mastitis detection is critical to minimise damage to the mammary gland and prevent the spread of infection within the herd. The following diagnostic tools are commonly used:

1. Visual Inspection: In cases of clinical mastitis, a simple visual inspection of the cow’s udder and milk can provide clues. Swelling, heat, and abnormalities in the milk are key indicators. Farmers should be trained to spot these early signs to ensure timely intervention.
2. California Mastitis Test (CMT): The CMT is a simple on-farm test that detects elevated levels of somatic cells in the milk, indicating inflammation. The test involves mixing milk with a reagent that reacts with somatic cells, creating a gel-like substance if the count is high. This test is highly effective for detecting subclinical mastitis in individual cows.
3. Somatic Cell Count (SCC): Somatic cell count is a key diagnostic indicator of udder health. A high SCC (above 200,000 cells per millilitre of milk) suggests the presence of infection, even if no physical symptoms are visible. SCC testing is often conducted in bulk tank milk to assess overall herd health, but individual cow SCC tests are more useful for pinpointing infected cows.
4. Bacterial Culture: This is the gold standard for diagnosing the pathogen causing mastitis. Milk samples are sent to a laboratory, such as FarmLab Diagnostics, where they are cultured to identify the bacteria involved. Understanding the pathogen responsible for the infection is essential for determining the appropriate treatment and managing future outbreaks.
5. Conductivity Testing: Some milking systems are equipped with sensors that measure the electrical conductivity of milk. An increase in conductivity may indicate a rise in sodium and chloride levels due to inflammation, suggesting mastitis. This method is often used in an automated milking system to monitor herd health in real-time.
6. PCR Testing: Polymerase Chain Reaction (PCR) testing is a highly sensitive method for detecting the DNA of mastitis-causing bacteria in milk samples. It’s particularly useful for identifying pathogens that may not grow well in traditional cultures, such as Mycoplasma.

Importance of Early Detection

Early detection of mastitis is essential to limit the severity of the infection and reduce its spread. When caught early, treatment is more effective, and the risk of permanent damage to the mammary gland is lower. In cases of subclinical mastitis, regular milk testing is vital for identifying infections that would otherwise go unnoticed.

Mastitis affects individual cows and the entire herd. Untreated infections can lead to chronic conditions that are harder to manage and may necessitate culling, leading to significant financial losses for the dairy farmer.

If you’re concerned about mastitis in your herd, early detection and accurate diagnosis are essential for minimising its impact. At FarmLab Diagnostics, we offer comprehensive testing services, including somatic cell count monitoring and bacterial culture analysis, to help you stay ahead of infections and maintain your herd’s health.