Mastitis is an inflammation of the udder that affects a high proportion of dairy cows around the world. Mastitis differs from most other animal diseases in that several different kinds of bacteria are capable of infecting the udder.
Cow health
These pathogens invade the udder through the teat canal, multiply, and produce harmful substances that result in inflammation, reduced milk production and altered milk quality. Mastitis leads to recurring economic losses in the dairy industry worldwide. A bacteriological diagnosis and proper selection of antibiotic based on antibiotic sensitivity are critical for rational and effective treatment of mastitis. Monitoring the success of the treatment is also valuable.
Mastitis is a costly disease (Halasa et al., 2007). On average, the losses caused by mastitis in The Netherlands range from €53 to €182 per subclinical case (Huijps et al., 2008). Besides economic losses, mastitis also leads to frustration for the farmer, a decrease in animal welfare and an increased risk of antibiotic residues. Excessive antibiotic use in animal farming is increasingly seen as a threat to public health, because it may lead to the emergence of multiple resistant bacteria. For both the prevention of mastitis and its treatment, it is critical to find out which pathogen is causing the problem.
The best way to prevent mastitis is by consistently implementing effective management practices, such as optimisation of nutrition, host resistance, environmental conditions, milking equipment, milking technique and hygiene (Huijps et al., 2010; LeBlanc et al., 2006). In addition, proper data handling and goal setting are crucial in disease prevention programmes. An increase in mastitis incidence usually occurs due to either an increase in infection pressure or a decrease in cows’ resistance. The latter can be caused by factors outside farmers’ control, but it usually indicates that farm management is not optimal.
Veterinarians can be important intermediaries in communication about udder health improvement. Regular veterinarian-farmer contact is a powerful factor because of the high frequency of service contacts. Other aspects include familiarity with each other’s context, personal characteristics, preferences, beliefs, aspirations and competencies that builds up over years, and the relationship of trust that develops. To be effective, a disease programme should do more than simply distribute technical information about best management practices. Prevention of complex diseases, such as mastitis, requires customised communication strategies, as well as an integrated approach between various stakeholders and different scientific disciplines. Think about FMS support, TSS support, support from nutritionists and veterinarians. Such programmes need to be prolonged and supported by a combination of several policy measures to change farm management consistently in the long run. Things like milk price, milk quota and financial incentives on milk quality norms, such as bonuses and penalties, have a strong influence on farmer mindset. It should therefore be taken into account that farmers are part of, and are influenced by, a wide societal and institutional context (Jansen, 2010).
Subclinical mastitis is most commonly recognised by detecting the inflammatory process in the udder by testing a sample of milk. Somatic cells are mainly leukocytes plus epithelial cells. An increase in the SCC tells us something about newly infected cows. We consider cows with fewer than 200,000 cells/ml to be healthy. For heifers the threshold is 100,000 cells/ml.
Mastitis can be defined as either clinical or subclinical. Detection of clinical mastitis is based on three parameters:
Grade 1: Mild. Milk secretion altered.
Grade 2: Moderate. Milk secretion and mammary glands altered.
Grade 3: Severe. Secretion, mammary glands and general state of health altered.
Sampling for microbiological analysis is one truly diagnostic method that allows us to identify the pathogen that is causing the disease. This gives us the opportunity to establish a protocol (treatment, vaccination, elimination, segregation) based on the result. We can use the Lely checklist on improving udder health for guidance. Dairy farmers should work closely with their herd veterinarian to help develop treatment protocols, provide oversight of appropriate drug use and monitor the success of treatment.
The quality of the results (and hence value for money) obtained from submitting a milk sample to the laboratory is to a very large extent determined by the quality of the initial sample. The advice is to take a sample of milk from each affected quarter a minimum of 6 hours after the last milking and to try to take a sample in a relatively clean area. Normally a minimum of ten samples per farm need to be taken in order to give an indication about the causing pathogen.
The teat end is often heavily contaminated by a range of environmental bacteria, and by normal commensal teat-end organisms. However, they are not necessarily the cause of the mastitis, so samples must be taken very carefully.
In summary: veterinarians are important intermediaries in communication about udder health improvement. Sampling for microbiological analysis is one truly diagnostic method that allows us to identify the pathogen that is causing disease. In the next article we will tell you more about contagious pathogens (cow-related) and environmental pathogens, as well as giving some practical guidance on preventing infection by these pathogens.
