Understanding Mastitis in Dairy Cows: Causes, Prevention, Diagnosis, and Treatment

Mastitis is primarily caused by bacterial infections that invade the udder tissue through the teat canal. The most common bacteria responsible include Staphylococcus aureus, Non aureus staphylococci and Escherichia coli. These pathogens can be found in the cow’s environment, on the skin of the udder, or even inside the teat canal. Once inside the udder, they multiply, causing inflammation and damage to the mammary tissue.

However, bacteria are not the only cause. Mastitis can also result from mechanical injury to the udder, which may occur due to over-milking, poorly maintained milking machines, or even injuries from other cows. Environmental factors, such as poor bedding hygiene or dirty barns, further increase the risk of mastitis as they expose the udder to harmful pathogens.

Mastitis is often classified into two types: clinical and subclinical. Clinical mastitis is visible and easy to identify, as the cow will show signs such as swelling, heat, redness, or pain in the udder, and the milk may appear watery or contain clots. Subclinical mastitis, on the other hand, presents no visible symptoms, making it more challenging to detect. However, it can still have a significant impact on milk production and quality.

Prevention of Mastitis

Preventing mastitis should be a top priority for every dairy farmer, as it is much easier and cost-effective to prevent the disease than to treat it once it has occurred. A comprehensive mastitis prevention programme should include proper hygiene, regular monitoring, and appropriate management practices.

1. Milking Hygiene: One of the most critical aspects of mastitis prevention is maintaining excellent hygiene during milking. The milking equipment must be cleaned and maintained regularly to prevent contamination with bacteria. It’s also essential to wash the cow’s udder and teats before milking, using disinfectant or pre-milking dips to kill any bacteria on the skin’s surface. After milking, post-milking teat dips should be applied to seal the teat canal and protect against bacterial invasion.
2. Bedding Management: Cows should be housed in a clean and dry environment. Wet, dirty bedding can harbour bacteria that can cause mastitis. Regularly cleaning and replacing bedding material, as well as ensuring proper ventilation in barns, will help reduce the risk of infection. If possible, deep straw bedding or sand bedding, which have better moisture management properties, should be considered.
3. Culling Chronic Cases: Some cows are more susceptible to recurring mastitis infections. Chronic cases should be identified and considered for culling, as they can be a source of infection for other cows in the herd. This is particularly important with some infectious agents such as Staphylococcus aureus which tend to persist in the other and become more difficult to treat as time progresses.  Culling these high-risk animals can significantly reduce the overall incidence of mastitis in the herd.
4. Dry Cow Therapy: Dry cow therapy involves administering long-acting antibiotics to cows at the end of their lactation period to treat any existing infections and prevent new ones during the dry period. This practice has been shown to significantly reduce the occurrence of mastitis in the subsequent lactation period. There is now an increased acceptance that antibiotics should be used selectively on infected cows at dry-off. 
5. Proper Nutrition: A balanced diet plays a vital role in maintaining the immune system of dairy cows. Cows with a strong immune system are less likely to contract infections, including mastitis. Ensuring that cows receive adequate levels of vitamins, minerals, and energy can help reduce the risk of disease.

Diagnosis of Mastitis

Early diagnosis of mastitis is crucial to prevent the spread of infection and minimise its impact on milk production. Farmers and veterinarians can use several methods to detect mastitis, particularly the subclinical form, which often goes unnoticed until milk production starts to drop.

1. Milk Somatic Cell Count (SCC): Somatic cells are white blood cells that increase in response to inflammation in the udder. An elevated SCC is one of the earliest signs of mastitis. Milk testing labs can provide SCC results for individual cows, allowing farmers to identify those with subclinical infections.
2. California Mastitis Test (CMT): This on-farm test involves mixing a small sample of milk with a reagent that causes the milk to thicken in response to the presence of somatic cells. A positive result indicates the presence of mastitis, even if the cow is not showing any visible symptoms.
3. Bacteriological Culture: In cases where mastitis is detected, it can be helpful to perform a bacteriological culture of the milk to identify the specific pathogen responsible. This information is valuable in selecting the most appropriate treatment and in understanding how the infection may have occurred. Recent advances with near-cow diagnostic methods such as the DairySmart system also are making this information more readily available.

Treatment of Mastitis

Treating mastitis depends on the severity of the infection and the causative pathogen. Veterinary intervention is often required, especially in severe cases. Treatment usually involves the use of antibiotics to target the bacteria causing the infection, as well as anti-inflammatory drugs to reduce pain and swelling in the udder.

1. Antibiotic Therapy: The type of antibiotic used will depend on the results of the bacteriological culture. Intramammary infusions (administered directly into the teat) are the most common form of antibiotic treatment for mastitis. In more severe cases, systemic antibiotics (given by injection) may also be necessary. It is crucial to follow the prescribed withdrawal period for antibiotics to ensure that no residues remain in the milk.
2. Supportive Care: Cows with mastitis should be monitored closely and provided with supportive care to help them recover. This may include pain relief, increased fluids, and, in some cases, removing milk from the infected quarter more frequently to reduce the bacterial load..
3. Severe Cases: In severe cases, such as when mastitis is caused by E. coli or other highly virulent bacteria, systemic symptoms such as fever, loss of appetite, and dehydration may occur. In these instances, immediate veterinary attention is required, and the cow may need intravenous fluids and intensive care.

Mastitis remains one of the most challenging health issues in dairy farming, but with proper management, hygiene, and early detection, the risks can be significantly reduced. Dairy farmers must remain vigilant, as early diagnosis and treatment can save both the cow and the farm from considerable economic loss. The key is to maintain a proactive approach, focusing on prevention strategies such as good milking practices, proper bedding management, and regular health monitoring.

If you suspect that mastitis may be an issue in your herd or would like to implement a more effective prevention programme, contact FarmLab today.

Let us help you keep your herd mastitis-free and your business thriving.