Winning the War on Mastitis and High SCC in Dairy Herds

By Tom Murphy, B&T Dairy Adviser, Teagasc, Galway/Clare

Did you know that a mild case of mastitis costs €200 and a severe case over €700, when all costs (including production losses) are included?  More milk is lost when the cow is infected in early lactation than when the infection occurs at a later stage. Research shows that over 50% of all mastitis cases occur in the first 100 days after calving.

In early lactation most mastitis and spikes in “Somatic Cell Counts” (SCC) are caused by “Environmental”, rather than “Milking Cow” mastitis infections. As the name suggests the spread occurs in the cows housing/calving environment rather than by the milking machine. Typically, the infection shows up soon after calving (not always in the first day), and usually inside the first four weeks. Whereas most “Milking cow mastitis” cases develop as the milking year progresses, which is caused by Staph aureus and is spread by the milking regime.

All herds are at risk of acquiring environmental mastitis in the two weeks either side of calving because at this time the cow’s immune system is at its lowest ebb.  Research has found that some cows teat ends never seal properly after drying off and in late pregnancy heifer teat ends (and also cows) often start to open as the udder ‘springs’ which makes them vulnerable to infection. Thus both cows and heifers are vulnerable to infection before calving. 

The Two principle types of bacteria most often associated with the mastitis that occurs shortly after calving are

• Streptococcus uberis - causing distinct clinical mastitis infection, where cows generally do not become very ill, but can result in very high SCC levels – typically 5-8,000,000 cells/ml.
• Coliform bacteria of which coli is the most widely known. These bacteria can cause severe mastitis often resulting in the loss of the affected quarter or even, the infected cow. 

Improving the environment of cows and heifers in late pregnancy reduces the incidence of these forms of mastitis.  Preventative farm management practices include

• Maintaining clean dry cubicle beds
• Cleaning cubicle passages twice daily from two weeks pre-calving
• Ensuring straw bedded calving areas (maternity ward) is ‘freshened up’ daily and that stale beds are removed frequently
• Teat spraying the cows 3 times a week in late pregnancy (in the last 3 weeks or so before planned calving) on farms where the problem is particularly prevalent
• Separating  freshly calved from pregnant cows(to reduce the risk of contamination of cubicle beds with discharges
• Letting freshly calved cows to grass as soon after calving as possible (Day four post-calving)

Well prepared and focused farmers practice a pro-active approach during the calving season, which has resulted in significant reductions of overall mastitis incidences as well as SCC herd levels and associated losses in recent years. On all Teagasc Dairy farms and increasingly on many commercial Dairy farms, the “California Mastitis Test” (CMT) is carried out on all cows at Day_4 post calving, before the freshly calved cow joins the main milking herd. CMT testing cows at this stage will have three potential outcomes:

1. CMT is clear and that cow is suitable for milking to the tank
2. CMT shows coagulation on all four quarters – this is more than likely stress related and associated with freshly calved heifers
3. CMT shows coagulation on one or two quarters. This indicates high SCC/infection of these quarters.

Category 2 cows need to be retested after a few days to confirm the result but clusters should be disinfected in the intervening time. Cows falling into category 3 animals will need treatment (assuming they haven’t a high SCC history) to address the issues identified, following treatment option-discussions with the vet. These cows should be milked last or clusters will need to be disinfected/flushed post milking to prevent any potential spread. If a cow does not respond to treatment, she should be culled, and prevented from spreading disease to the herd.

Most Dairy farmers have now realized the importance of milk recording as an overall aid to Dairy herd management. It is now an essential tool in managing the “Dry cow therapy” programme and in adhering to Anti-Microbial Resistance requirements on the Dairy farm. However, the first recording should take place by mid to late March (depending on calving start date), to accurately assess the success or otherwise of the previous Dry cow therapy programme.

A number of very useful reports are compiled through ICBF and Herdplus which can be used by the farmer (sometimes in conjunction with the Vet & Advisor) to improve the mastitis/SCC status of the herd. Persistently high SCC cows (reading > 200,000 SCC/ml for two or more concurrent tests) from previous years are candidates for immediate culling if they test high in the first milk recording.

Removing the problem offenders as early as possible in the year has been shown to significantly improve the ongoing mastitis status of herds and a reduction in herd SCC. This in turn has delivered on increased milksolids production, less work and reduced costs.

Despite the current demanding workload, now is possibly the most important time of the year to revise the farm programme and ensure that all battles are won in the war on mastitis.