Treatment of Subclinical Mastitis

Take home message:

• It is possible to achieve satisfactory cure rates using intramammary antibiotics for treatment of subclinical mastitis during the lactation period but the cost effectiveness of the treatments will vary depending on herd & cow specific factors
• Treatment of subclinical mastitis during lactation is not generally cost effective for herds that are able to effectively reduce transmission of contagious pathogens unless there is an alternative use of the milk that would be discarded
• If treatment is undertaken, cow specific risk factors should be considered to identify cows that are most likely to respond to treatment

Mastitis occurs in both a clinical and subclinical form. Clinical mastitis is readily apparent and treatment decisions for it are generally motivated by a desire to return milk to a saleable state. Detection of subclinical mastitis is more difficult and the use of indirect tests (such as counting somatic cells or bacteriological analysis of milk samples) is necessary. Subclinical mastitis is often undetected and therefore has the greatest economic impact.

With the exception of infections caused by Streptococcus agalactiae, treatment of cows diagnosed with subclinical mastitis is usually discouraged because discard of saleable milk results in financial loss. However, there are negative outcomes that result from having cows affected with subclinical mastitis in the dairy herd and many progressive dairy managers are interested in determining the impact of treatment. The potential benefit of treatment is especially relevant for herds that use pasteurizers and feed waste milk to calves.

Several recent studies have evaluated the impact of treatment of subclinical mastitis and all have confirmed that the most important step is to first identify the type of pathogen that is most frequently associated with subclinical cases on the individual farm. The only way to definitively identify mastitis pathogens is to collect aseptic milk samples for microbiological examination. Recent research has also reinforced the importance of focusing first on reducing transmission of mastitis as the long term impact of treatment will only be effective if prevention is effective. Finally, treatment is only effective for cows with specific characteristics and therefore treatment of subclinical mastitis should be targeted based on specific characteristics of cows, pathogens and individual herds. Read the full article here.