MORE THAN $150 million is lost to Australian dairy farmers each year through poor udder health.
Mastitis is the major cause of this loss as it reduces milk yield and leads to poor quality milk.
The investigation of mastitis does not rely on the results of culture alone. A history of bulk milk cell count (BMCC), individual cow cell counts (ICCC) and history of the cows affected including clinical cases and treatments, all contribute to the investigation and subsequent recommendations.
However, knowledge of the major organisms that are causing clinical mastitis within a herd allows informed decisions to be made regarding treatment and control options.
Treatment vs diagnosis
The vast majority of clinical mastitis cases are treated by dairy farmers without definitive knowledge of the causative organism. The most common reasons for submission of samples for culture are:
If there has been an increase in the incidence of clinical cases of mastitis
If there has been a sudden increase in BMCC
If there has been failure of response to treatment by any given individual or group of individuals
Commercial laboratories are commonly used for the culture of mastitis pathogens and can provide microbiological expertise when interpreting the results.
However, there is often an associated time-delay between sample submission and feedback to the farmer.
This time delay can lead to decreased motivation and subsequent action by the referring veterinarian and the farmer. Research has shown that the benefit of antibiotic sensitivity testing at commercial laboratories is debatable for bovine mastitis pathogens.
In practice this means that an antibiotic that is found to be effective in the laboratory will not necessarily be effective in the cow.
On-farm options for mastitis culture
On-farm rapid-culture systems offer the option of reducing the time delay between submitting samples and obtaining results.
An example of such a system includes the Farm Medix CHECK-UP® Mastitis Diagnostic Tool.
With training and on-going monitoring, this can be used on-farm and allows differentiation and isolation of different common strains of Streptococcus, Staphylococcus, E.coli, Klebsiella, Proteus and Pseudomonas indicated in bovine mastitis.
Prompt knowledge of a specific mastitis pathogen allows strategic management decisions to be made including selection of antibiotic therapy, drying off, culling or change in milking routine.
A recent New Zealand study showed that on-farm culture and selective antibiotic therapy can be implemented successfully on-farm.
This research demonstrated that there was a 25 per cent lower antibiotic usage where selective antibiotic therapy was used based on culture result.
However there was no difference in the proportion of cows that needed to be re-treated for mastitis (between the selective antibiotic cows and blanket antibiotic cows).
The major advantage of on-farm culture systems is the rapid turn-around time.
Samples are quick and easy to prepare and the majority of results are available within 24 hours.
Some veterinary clinics are utilizing this system to provide this service for their clients.
Alternatively, the cultures can be performed on-farm although specific training by your veterinarian will be required.
It is important to be aware that such on-farm culture systems do not have the capability of diagnosing Streptococcus agalactiae or Mycoplasma.
It is strongly recommended to submit both a bulk milk and hospital milk sample to a commercial laboratory to rule out these pathogens.
In summary, there is potential for on-farm rapid-culture systems to reduce antibiotic usage in the treatment of clinical mastitis and to identify animals with infections where treatment is likely to be futile.
This not only guides our treatment decisions but is also more cost-effective in the long term.
• Gemma Chuck is an adviser with Apiam Animal Health.