Culture to Cull

We certainly appreciate there are difficulties in removing culls from farm with the current Covid situation, but if you do get the opportunity how do you decide which cows to cull for udder health reasons?

Traditionally we have relied on a combination of information such as age, BW/PW, production, somatic cell count (SCC), number of SCC >150,000 cells/ml exceeded during lactation, number of mastitis cases etc. Consider the following animals:

Based on this information, if you had the opportunity to cull 5 cows based on this information, which ones would you choose? Let’s review those decisions when we include the milk culture result:

Hopefully you will see that, with the milk culture result included in the decision-making process, cows 6, 9 and 10 in particular should be ones prioritised for culling. Recently we had the opportunity to culture a large group of animals after a recent herd test. If we just had a look at the results from cows with a SCC greater than 500,000 cells/ml:

Now let’s compare these results compared to culturing all cows with a SCC >150,000 cells/ml:

As you can see, if we just collected a sample from animals with SCC above 500,000cells/ml we would have missed 18 out of the 30 cows with Staph aureus.

The other added benefit of culturing is that if we did this shortly before dry off, we could consider not using antibiotic dry cow therapy in cows with no bacteria detected on the culture (in this case just over 50% of animals).

We are conducting some very exciting research in this area for this dry off period so watch this space!!