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.

Mastitis in dairy cattle is the persistent, inflammatory reaction of the udder tissue. Mastitis, a potentially fatal mammary gland infection, is the most common disease in dairy cattle in the United States. It is also the most costly to the dairy industry. Milk from cows suffering from mastitis has an increased somatic cell count.

Definition

Mastitis occurs when white blood cells (leukocytes) are released into the mammary gland, usually in response to bacteria invading the teat canal. Milk-secreting tissue and various ducts throughout the mammary gland are damaged due to toxins released by the bacteria. Mastitis can also occur as a result of chemical, mechanical, or thermal injury.

Identification

File:Mamite grangrin moirt pés.JPG

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 subclinical mastitis, a cow does not show any visible signs of infection.

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:

2

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

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.

Effects on milk composition

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

Mastitis can cause a decline in potassium and 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

File:California Mastitis Test Schalmtestplatte.jpg

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. Vaccinations for mastitis do exist, but as they only reduce the severity of the condition, and do not prevent new infection 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 dung and urine.

Industry costs

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

Further reading

• Harmon, R. J. 1994. Physiology of mastitis and factors affecting somatic cell counts. J. Dairy Sci. 77:2103-2112.
• Jones, G. M., R. E. Pearson, G. A. Clabaugh, and C. W. Heald. 1984. Relationships between somatic cell counts and milk production. J. Dairy Sci. 67:1823-1831.
• Myllys, V., and H. Rautala. 1995. Characterization of clinical mastitis in primiparous heifers. J. Dairy Sci. 78:538-545.
• National Mastitis Council. 1996. Current Concepts of Bovine Mastitis, 4th ed., Arlington, VA.
• Fox LK et al. Survey of intramammary infections in dairy heifers at breeding age and first parturition. J Dairy Sci. 78; 1619–1628, 1995.
• Hallberg JW et al. The visual appearance and somatic cell count of mammary secretions collected from primigravid heifers during gestation and early postpartum. J Dairy Sci. 78; 1629-1636.
• Hogan JS et al. Efficacy of an Escherichia coli J5 bacterin administered to primigravid heifers. J Dairy Sci. 82; 939-943, 1999.
• Nickerson SC. Mastitis and its control in heifers and dry cows. International Symposium on Bovine Mastitis. Indianapolis, IN, September, 1990. pp 82–91.
• Nickerson SC et al. Mastitis in dairy heifers: Initial studies on prevalence and control. J Dairy Sci. 78;1607–1618, 1995.
• Nickerson SC et al. Efficacy of s Staphylococcus aureus bacterin in dairy herifers. An update. Proceeding of the Nat Mastitis Council Meeting. 295-6, 1998.
• Sears PM and Wilson DJ. Heifer mastitis. Bov Practitioner 28; 56-58, 1994.

External links

• UC Davis fact sheet
• NMC - Global organization for mastitis control and milk quality