By Product Management, Nuscience

Mastitis is the most expensive, often recurrent, disease in dairy farming. The inconvenience and costs associated with clinical mastitis are most visible. However, subclinical mastitis (cows with elevated somatic cell count) is responsible for the greatest losses (reduced milk production, fines, etc.). This has already been the subject of long-standing attention through the 10-point programme. This comprises measures for the prevention and control of mastitis, supplemented by guidelines for comfort, hygiene and housing. Still, a very big amount of preventive and curative antibiotics are used in the battle against mastitis worldwide.  In order to reduce this antibiotic use, and thus antibiotic resistance, it is crucial to support the cow’s own immune system!

Two stressful periodes

The prevalence of new infections of the mammary gland shows two peaks: at drying off and after calving, two extremely stressful periods for the cow. At drying off, milk production is still relatively high, there is an increased risk of milk leakage: the pressure in the udder increases and the teat entrance remains open during the first days of the dry period. That is when bacteria will seize their chance to infect the udder. The second vulnerable period is of course situated around calving. Immunosuppression in this transition period (Figure 1) is thought to be caused by oxidative stress as a major underlying factor. Additionally, high productive cows can already start leaking milk because the teat entrance are opening up which can easily lead to new infections.

Antibiotics under discussion

Antibiotics have become an integral part of today’s livestock production, including dairy cattle. The indiscriminate use of antibiotics in animal agriculture has been subjected to a critical scrutiny by governments but also by consumers. Consumers worldwide increasingly want healthy food from antibiotic-free raised animals, preserving for as long as possible the ever-diminishing arsenal of antimicrobials effective in humans. How can we responsibly use antibiotics in animals without compromising food safety and human health, as well as animal health, welfare and productivity?

Targeted antibiotic treatment

Since 1969 the standard recommendation was to use antibiotics when drying off cows. However, this old habit is encountering opposition. In the Netherlands for example, preventive use of antibiotics when drying off has already been banned since 2012. Today farmers are only allowed to use antibiotics on cows that are at increased risk of developing mastitis: so-called dry cow therapy. The tipping point between an acceptable increase of udder inflammation and a reduced use of antibiotics is considered at a somatic cell count of 150,000 cells/ml for heifers and a somatic cell count of 50,000 cells/ml for older cows, no more than four weeks before drying off, as found at the last milk recording.  

Immunity is key

Around the world selective dry cow therapy is gaining interest. Any targeted antibiotic treatment like described above can only be an effective strategy to reduce antibiotic use provided that it is combined both with optimised management practices and optimal nutrition. This combined strategy can successfully result in a reduction of prophylactic antibiotic use without an excessive increase of curative use of antibiotics because of clinical or subclinical mastitis. 

As indicated earlier in this paper it is important that the milk production at drying off is not too high in order to prevent milk leakage. A lower milk yield (< 12 kg) can be achieved by feeding a low-protein ration, since protein is the driver behind milk...