What is milk culturing?
Virtually all cases of mastitis are caused by bacterial infections of the udder. It is however not possible to tell which bacteria are responsible for the infection by the changes in the milk, udder or cell counts.
A milk sample can be cultured to identify the bacteria causing a case of mastitis and the sensitivity to various antibiotics. Traditionally this had to be done at a commercial laboratory with turnaround times of 3 to 4 days, however, we can now perform milk culture and antibiotic sensitivity testing in our clinics at Foster, Leongatha and Wonthaggi with a 24-hour turnaround time.
Costs for a culture and sensitivity (inc GST) are $25 for a single sample, $24.25 for 2 – 4 samples, $23.75 for 5 – 8 samples and $23.00 for 9 or more samples.
When should you perform milk cultures?
Milk culturing is recommended whenever a herd problem with mastitis emerges – either more clinical cases than expected (more than 5 cases / 100 cows / month) or if BMCCs are rising unexpectedly. It is important in these situations to know which bacteria are involved as this allows us to pinpoint the likely causes and select appropriate management strategies.
It is a good policy to sample all cases of clinical mastitis and freeze the samples. If the cow does not respond to treatment or you are worried about an outbreak – the frozen samples can be cultured. If an on-farm milk culturing system is being used – all clinical cases of mastitis are first cultured and the bacterial antibiotic sensitivity is determined before deciding on a treatment plan.
High cell count cows can also be cultured if your BMCC is rising without any increase in the number of clinical cases. We still need to send these samples to the lab for culture as they often contain only very low numbers of bacteria and can be difficult to culture.
How do I take a good sample?
As milk is a great medium for growing bacteria, any contamination of a sample will lead to confusing culture results. Sterile sample bottles must be used, teat ends must be disinfected with 70 % alcohol prior to sampling and care must be taken to avoid contaminating the sample with any dirt / manure / skin flakes that may be knocked off the teat or udder. Countdown 2020 has a good description of milk sampling best practice.
If you are looking for more information on milk culturing (either at the clinic or on-farm systems) or mastitis in general, please contact one of our clinics and speak to one of our vets.