Drying-off: Getting to know the bacteria on your farm

Ahead of drying-off cows, which on many farms will begin later this month, it is a good idea to determine the amount the bacteria you are dealing with.

Farms are now required to use selective dry cow therapy (SDCT) on their cows, but some cows are still going to need an antibiotic during drying-off.

Getting a culture and sensitivity test is a good idea ahead of drying-off, as it provides you with a better understanding of the bacteria at hand.

Drying-off

The test should give you a better picture of the bacteria causing mastitis/cell count issues on your farm.

You can then (with the consultation of your vet), select the antibiotics that will work best in your herd.

A culture and sensitivity test involves growing bacteria on a plate in a lab, which takes 48 hours. It then needs to be tested, which takes a further 12 hours. In total, test results will take three days.

It may be especially useful on farms where there has been an increase in mastitis cases/cell count issues.

Using milk recording data, you can identify cows that have cell count issues, or use records to identify cows that have mastitis during the most recent lactation.

You can then use the California Mastitis Test (CMT) to determine which quarter is at fault and take a sample.

Not every cow needs to be tested, but more than one cow should have a sample taken to ensure you are getting an accurate picture.

CMT

Although milk recording data will highlight any cows that may have an issue, it does not indicate which quarter or quarters.

It is quite possible that one quarter on a cow is significantly higher than the others and this is causing that cow’s cell count to spike.

Using the CMT, you can identify which quarter is at fault using real-time information.

The procedure for using the CMT kit is very simple:

Draw and discard the first three draws and then fill each well with a quantity of milk. Try to avoid cross-contamination;
Once all four wells have a quantity of milk, tilt the tray to a 45º – this will ensure there is an equal volume of milk in all four wells;
Turn the tray back flat and squeeze the bottle until an equal quantity is applied to all four wells; there should be an approx. 50:50 mix of milk and reagent;
Stir the tray for 30 seconds and watch for any changes to the consistency of the solution. The degree of thickness reflects how high the somatic cell count (SCC) level is within the quarter.