Mastitis In Dairy Cattle

Gangrenous mastitis in a cow after 10 days. Green arrow indicates complete necrosis of the teat. Yellow arrows indicate the limits of the gangrenous tissue, but the necrotic area is not well delimited on the upper part of the udder.

Dairy cow with gangrenous mastitis . rear quarter

Bovine mastitis is the persistent, inflammatory reaction of the udder tissue due to physical trauma or microorganisms infections. Mastitis, a potentially fatal mammary gland infection, is the most common disease in dairy cattle in the United States and worldwide. It is also the most costly disease to the dairy industry. Milk from cows suffering from mastitis has an increased somatic cell count. Prevention and Control of mastitis requires consistency in sanitizing the cow barn facilities, proper milking procedure and segregation of infected animals. Treatment of the disease is carried out by penicillin injection in combination with sulphar drug.

Definition

Mastitis occurs when white blood cells (leukocytes) are released into the mammary gland, usually in response to bacteria invading the teat canal or occasionally by chemical, mechanical, or thermal trauma on the udder. Milk-secreting tissue and various ducts throughout the mammary gland are damaged due to toxins released by the bacteria resulting in reduced milk yield and quality.

Identification

the quarter with Gangrenous mastitis

A gangrened udder (which sloughed naturally)

This disease can be identified by abnormalities in the udder such as swelling, heat, redness, hardness, or pain (if it is clinical). Other indications of mastitis may be abnormalities in milk such as a watery appearance, flakes, or clots. When infected with sub-clinical mastitis, a cow does not show any visible signs of infection or abnormalities in milk or on the udder.

Mastitis-causing bacteria

Bacterial cells of Staphylococcus aureus, one of the causal agents of mastitis in dairy cows. Its large capsule protects the organism from attack by the cow's immunological defenses.

Bacteria that are known to cause mastitis include:

These bacteria can be classified as environmental or contagious depending on mode and source of transmission.

Types of mastitis

Mastitis may be classified according two different criteria: either according to the clinical symptoms or depending on the mode of transmission.

Clinical symptoms

• Clinical mastitis
• Sub-Clinical mastitis
• per acute mastitis
• acute mastitis
• sub acute mastitis
• chronic mastitis

Mode of transmission

• Contagious mastitis
• environmental mastitis

Transmission

Mastitis is most often transmitted by repetitive contact with the milking machine, and through contaminated hands or materials.

Another route is via the oral-to-udder transmission among calves. Feeding calves on milk may introduce some mastitis causing bacteria strain in the oral cavity of the calf where it will stay dormant until it is transmitted elsewhere. Since grouped calves like to stimulate suckling, they will transmit the bacteria to the udder tissue of their fellow calves. The bacteria will lay dormant in the udder tissue as the calf grows until it begins to lactate. That is when the bacteria activates and causes mastitis. This calls for strict calf management practices to curb this route of transmission.

Effects on milk composition

Serous exudate from udder in E. coli mastitis in cow (left), in comparison to normal milk (right)

Mastitis can cause a decline in potassium and an increase in lactoferrin. It also results in decreased casein, the major protein in milk. As most calcium in milk is associated with casein, the disruption of casein synthesis contributes to lowered calcium in milk. The milk protein continues to undergo further deterioration during processing and storage. Milk from cows with mastitis also has a higher somatic cell count. Generally speaking, the higher the somatic cell count, the lower the milk quality.

Management

Detection

A plastic paddle used in the California mastitis test.

Cattle affected by mastitis can be detected by examining the udder for inflammation and swelling, or by observing the consistency of the milk, which will often develop clots or change color when a cow is infected.

Another method of detection is the California mastitis test, which is designed to measure the milk's somatic cell count as a means for detecting inflammation and infection of the udder.

Treatment

Treatment is possible with long-acting antibiotics, but milk from such cows is not marketable until drug residues have left the cow's system. Antibiotics may be systemic (injected into the body), or they may be forced upwards into the teat through the teat canal (intramammary infusion). Cows being treated may be marked with tape to alert dairy workers, and their milk is syphoned off and discarded. To determine whether the levels of antibiotic residuals are within regulatory requirements, special tests exist. Vaccinations for mastitis are available, but as they only reduce the severity of the condition, and cannot prevent reoccurring infections, they should be used in conjunction with a mastitis prevention program.

Control

Practices such as good nutrition, proper milking hygiene, and the culling of chronically infected cows can help. Ensuring that cows have clean, dry bedding decreases the risk of infection and transmission. Dairy workers should wear rubber gloves while milking, and machines should be cleaned regularly to decrease the incidence of transmission.

Prevention

A good milking routine is vital. This usually consists of applying a pre-milking teat dip or spray, such as an iodine spray, and wiping teats dry prior to milking. The milking machine is then applied. After milking, the teats can be cleaned again to remove any growth medium for bacteria. A post milking product such as iodine-propylene glycol dip is used as a disinfectant and a barrier between the open teat and the bacteria in the air. Mastitis can occur after milking because the teat holes close after 15 minutes if the animal sits in a dirty place with feces and urine.

Industry costs

This disease costs the US dairy industry about 1.7 to 2 billion USD each year.