Make sense of your cell count

Photo by Geoff Adams

I have had a few discussions in recent weeks with farmers who are struggling to remain in premium cell count and how they might be able to manage a cell count issue.

As always, I remind them that unless we know exactly what we are dealing with, it is hard to make a sound plan.

In many cases, the first contact that I have is when the BMCC is already out of premium and the farmer is desperate to get back under whatever their factory requires.

Equally as often, I am faced with a dreadful lack of information on which to base my advice and so we start a process of investigation because there is unfortunately no ‘one size fits all’ approach to managing a persistently high BMCC.

Firstly, I need to know whether the high cell count is associated with clinical mastitis (cows presenting with abnormal milk) or whether the infection is sub clinical (the cows have an intramammary infection but do not show clinical signs) or whether both problems are occurring concurrently.

Many (most?) herds in my experience keep records of clinical mastitis cases, but that information is frequently not in a readily available form to analyse.

Herd recording where individual cell counts are available for each cow is now only available in the minority of herds.

It is much less common for herds to have culture or other testing results that identifies the causative agent in their clinical mastitis and it is exceptionally rare for herds to have culture results from sub clinically infected animals at the beginning of an investigation

In other parts of the world, clinical diagnostics and herd screening prior to dry-off is becoming far more common and forms a pillar of the responsible use of antimicrobials in those countries and I would love to see us following this lead.

I usually start by screening the bulk tank with a PCR test to look for mastitis pathogens and to determine whether the common contagious pathogens are present.

I usually also take advantage of this opportunity to check the herd antibody levels for BVDV and if indicated check for PI animals in the milking herd.

It is essential to ensure that the milking machines are tested and in optimal condition and that all important rubberware is replaced regularly according to the manufacturer’s recommendations

Next, I encourage collection of high quality samples for culture from any clinical mastitis cases, while I organise a herd ‘spot’ test (assuming ISCC data is not available).

I usually spend a little time showing how a high quality clean sample can be collected for milk culture because poorly collected samples are an expensive waste of time if all that you grow are contaminants.

If the farmer is unwilling or unable to perform a herd test, it is possible to ‘paddle test’ the herd using the California Mastitis Test (CMT) to try to identify the high cell count cows.

Either way, once I have identified the highest cell count cows, collecting a sample for culture is the next move.

I like to test a minimum of 10 but ideally 15 to 20 high cell count cows to determine what is the bacteria responsible for the sub clinically infected cows

Once I have an idea whether the problem is predominantly environmental bacteria or contagious bacteria we are much better placed to determine what the next best move will be.

On farms where the high cell count cows are predominantly environmental, it is essential that we look for (and address) the environmental factors that we can manage or control and implement some preventative plans to reduce new infections from the environment.

When the infections are caused by contagious mastitis pathogens, it is essential that we develop plans that will reduce exposure of uninfected animals to the infected animals to prevent spread during the milking process.

Looking for damaged, rough or swollen teat ends is an important part of the investigation to determine if over-milking or vacuum/pulsation issues may be present.

Recently, I have been using some high-tech gadgets that measure milk flow, teat end vacuum and pulsation during milking and these can give me information on how the milking machines and the staff are performing when the machines are in use.

Teat spray application and concentration are checked and corrected if necessary.

Ultimately, the important message is that unless we identify the causes of high BMCC, we cannot implement the best prevention and treatment strategies.

Culling and drying off infected cows plays a part, but unless we identify the cause, prevent new infections from the environment or from contagious animals and manage milking routines to reduce risks, the same pattern of cell count creep will occur every year causing unnecessary stress and loss.

Dr Robert (Rob) Bonanno is the Regional Veterinary Lead for ProDairy in Gippsland and northern Victoria.