Mastitis

Mastitis is defined as an inflammation of the mammary gland. Pathogenic microorganisms enter the udder through the teat canal, overcome the cow´s immune system and multiply in the udder. Toxins are produced that are harmful to the mammary gland. Consequently, the milk composition changes and milk yield decreases.

 

There are two main types of mastitis: a clinical and a subclinical form. While symptoms are seen if the clinical form is predominant - e.g. a swollen and hot udder – no clinical signs are seen for the subclinical form, making the latter one hard to identify.

 

Bacteria are the main causativemicroorganisms. Major pathogens are Staphylococcus aureus, Streptococci (agalactiae, dysgalacticae, uberis), Escheria coli and Klebsiella spp.

 

Hudson et al. (2012) surveyed 80 dairy herds. In 10,096 out of 39,590 observed lactations, they found at least one clinical mastitis between the 20th and 220th day of lactation. This means, that approx. 25% of cows will suffer from clinical mastitis – while the incidence for subclinical mastitis is thought to be even higher!

 

Multiparous cows are generally at a higher risk of developing clinical mastitis than first-calving cows. While the risk for a clinical mastitis is highest in early lactation (Steeneveld et al., 2008), the risk for a subclinical mastitis increases with ongoing lactation. Additionally, cows with a high milk yield are more vulnerable to develop a mastitis – regardless of the form – than cows with a lower milk yield.

 

A clinical mastitis is combined with pain and a severely decreased well-being of the animal. For the farmer, a series of consequences will follow a mastitis: First of all: direct costs for medical treatments arise. In Sweden, a veterinarian charges on average 119€ for a clinical mastitis treatment (Nielsen, 2009). But the veterinarian costs are only the tip of the iceberg: yield loss (up to 10%; Fehlings et al., 2012), an altered milk composition, discarded milk extra labour and subsequent disorders – including decreased fertility – add to the severity of the suffered economical losses. Nielsen (2009) assumes that the average economic loss per case of clinical mastitis are 275€. For a subclinical mastitis the author states cost of about 60€ per case.

 

Bacteriological cultures of milk and the presence of pathogens herein offer a diagnostic possibility.

 

Nonetheless, itis not feasible as a routine test (Nielsen, 2009). The practical solution is to measure the somatic cell count (SCC) as milk always contains a certain amount of somatic cells. Normally, leukocytes dominate the somatic cells in a healthy and lactating mammary gland. If a bacterial infection occurs, neutrophils will increase dramatically as well as the total SCC. Hence, the SCC is an indicator for udder health. The lower the SCC, the better is the health status of the cow. A SCC threshold of 100,000 cells/ml is internationally accepted as safe for consumer and a SCC < 100,000 cells/ml is rewarded by the dairy industry with a quality bonus, while a SCC of 200,000 cells/ml will already lead to a decreased milk yield of 6% (Fehlings et al., 2012)!

 

 

Several measures can be taken to minimize mastitis: next to a consequent dry-cow management, hygiene is a tremendous tool in the fight of mastitis – including clean udders, the use of milkers´ gloves, clean bedding and a good milking management. Furthermore, the right feeding strategy can help cows to achieve both – a high milk yield and a healthy udder. Selected phytogenic feed additives support these goals.