How data analysis helped dairy herds cut mastitis cases

A project involving multiple dairy farms across Wales has demonstrated why collecting data to establish the mastitis “red flags” specific to an individual herd can be key to reducing disease incidence.

Farming Connect enlisted 10 herds across mid, south and west Wales to work with veterinary consultant James Breen to research the value of using data to work out mastitis and somatic cell count (SCC) patterns and their causes.

James supported each farm with expert advice on how to reduce their incidence of clinical and subclinical mastitis.

See also: What are the most common causes of mastitis in UK herds?

Industry reports generally put the mastitis incidence in UK herds at an average of 30-35 cases in every 100 cows. Farm consultant Anna Bowen, of the Andersons Centre, calculates that in a 150-cow herd, this equates to between 23 and 53 cases a year.

At an estimated cost of £314 for each case of clinical mastitis (the figure used in the 2024 Kingshay Dairy Costings Report), the annual financial loss to that herd would be £7,222-£16,642.

“While achieving zero incidence of mastitis is unrealistic, there are significant financial benefits to reducing incidence – plus the welfare benefits, positives for public perception of agriculture, and the potential knock-on effects of reducing antimicrobial usage,” says Anna.

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Mastitis infection pattern

The project farms, which ranged in scale from small to large herds, supplied James with SCC and clinical mastitis data. He used the Mastitis Pattern Analysis Tool (MPAT), developed by Quality Milk Management Services (QMMS) and the University of Nottingham, to analyse these data.

“This allowed each herd to establish the predominant mastitis infection ‘pattern’ in the past three months, alongside analysis of new infection rates and incidence rate of clinical mastitis events,’’ he explains.

Further information on cure rates, dry period new infection rates, and incidence rates in heifers, could also be calculated where the data supported it.

At every data collection stage, the farmers were made aware of where the dry period and lactation cases had originated, and the infection rates in their heifers.

Sampling technique

Crucial to the project was sampling the milk from cows with clinical mastitis to establish the bacteria responsible for the infection.

The most common mastitis pathogen was Streptococcus uberis, followed by E coli, while seven samples grew Aerococcus viridans, a Gram-positive bacterium (tests positive to a Gram stain test, indicating thick cell walls) of increasing importance.

Anna, who collated the project findings, says the sampling process highlighted how important it was that samples were taken in hygienic conditions.

“Of the 53 samples submitted, nearly a quarter were contaminated and so were effectively wasted samples,” she says. “This usually happens due to poor collection technique.”

Sampling is important because when the mastitis-causing pathogens on a farm are known, appropriate treatments can be used, she added.

The data showed that none of the farms had contagious mastitis – all showed an environmental pattern that either originated in the dry period or during lactation.

The incidence of mastitis ranged from one farm with two cases in every 100 cows in the spring, to another with 104 cases in every 100 cows in winter.

Recommended interventions

Anna says some of the differences were due to improved recording, while others reflected the farm’s disease pattern.

Among the interventions James recommended to some of the farms were those dealing with housing, bedding, and the milking routine, with ventilation, manure management and stocking rates key areas for attention.

One farm was advised to open the ends of a shed to improve air and cow flow and increase the loafing area. More frequent scraping was suggested, together with repairs to prevent slurry from pooling, and a reduction in the stocking rate among the high-lactation group.

For another farm, where mastitis originated in the dry period, James suggested more frequent moves of dry cows at grass.

The stocking rate in this farm’s dry cow shed was too high, and ventilation was insufficient, so the farmer was advised to open up the roof ridge to improve ventilation and to bed down more frequently.

A further recommendation was to consider the use of portable cubicles to reduce the stocking rate.

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Sustained effort

Anna says while mastitis incidence on some of the farms reduced during the 12-month project, on others it had increased. She points out that many udder health issues take “considerable effort” to resolve and that time is also a factor.

“It may, for example, need a year to pass so that winter housing can be assessed, changed, and the cows then pass through the housed period, before data is available,” she says.

The farms that saw the most positive results were those that worked with their vets to reduce incidence. For example, one farm managed to reduce its rolling SCC from 310,000 cells/ml to 262,000 cells/ml.

Putting a financial value on SCCs is difficult as it depends on the levels at which penalties and bonuses are imposed in individual milk contracts, and the value of those, says Anna.

“One of the farms has penalties imposed at a fairly low SCC, and produces a large volume of milk, therefore an extra 0.5 p/litre is a significant sum of money and would quickly pay for the changes recommended by James.

“In contrast, another has no penalties or bonuses until SCCs are exceptionally high, and is a very small herd, so 0.5p/litre is a much smaller sum of money.

“However, in a small herd, there is less of a dilution, so stopping one cow having a high SCC, or curing her during the dry period, may have a big impact on the herd’s overall bulk milk SCC.”