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Virginia Cooperative Extension - Knowledge for the CommonWealth

What's in you tank?

Dairy Pipeline: March 2006

Sue Puffenbarger
Dairy Science Extension Agent
Franklin County
(540) 483-5161 email:

I'm regularly called to farms to help with somatic cell count and mastitis issues. This is generally a very challenging issue as there are so many factors that affect udder health. An effective, but under-utilized, tool for monitoring your herd's bacterial organism status is bulk milk tank testing. In this instance, I am referring to monthly bulk tank sampling to identify the predominant mastitis organisms in your herd. With a quick turnaround time and less cost than sampling individual cows, this provides a snapshot of what is going on in your herd.

By monitoring monthly, you can make your veterinarian or consultant's job easier. Are certain organisms predominant in the summer versus the winter? Have you switched from dry sawdust to green? Oak to Pine? Is your recycled sand clean enough? Are you dealing with Environmental Streps. or contagious organisms like Staph. Aureus, Strep. Ag. Or Mycoplasma? Have you switched teat dips? Somatic Cells Counts are a great starting point, but until you know what you are dealing with at a herd level, how do you know you are treating with the most effective antibiotic? By knowing which organisms you are dealing with, you can make better management decisions.

Samples should be taken as aseptically as possible. Agitate the milk for at least 10 minutes and collect at least two ounces of milk from the top of the bulk tank using a sanitized dipper. Use either a flip top container, like those used for DHIA samples, or a Whirl-pak. Label and refrigerate samples IMMEDIATELY, then transport to the lab on ice.

When troubleshooting a current problem, multiple samples are needed and it is recommended that you take three or four samples from different pickups. Freeze the samples until they can be delivered to the lab. One thing to note--somatic cell counts can not be obtained on samples that have been frozen. It is also best to use fresh rather than frozen samples when testing for mycoplasma. Samples can be sent to your Virginia Department of Agriculture State Lab or--in some cases--your veterinarian for analysis. Cost usually runs $6 - 10 per sample to test for basic mastitis organisms.

Bulk tank sample analysis should not be used to make treatment decisions. Results from the bulk tank samples should be used along with your monthly DHIA

Cell Count data to identify which individual or groups of cows to sample so you can make better choices on which treatment to use or which management practices need to be modified. With the volatility in the price of milk, can you afford NOT to monitor your bulk tank to stay ahead of problems?

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