Getting the most value from your first herd test

Getting the most value from your first herd test
By Sam Foss, Veterinarian, Anexa Vets Te Aroha

We recommend spending some time going through your first herd test results and identifying the cows with the highest somatic cell counts (SCC) that are likely to have subclinical mastitis. At the time of your first herd test (around peak lactation) your herd should have its lowest BTSCC. Now is a good time to take action and identify potential problems as these can snowball if left unchecked. By correcting any problems early, you are able to maintain the lower BTSCC , giving you more options in later lactation including OAD milking and dry cow strategies.

So, what do you need to do?

Identify cows with the highest SCC; the absolute SCC you use as a threshold will depend on how many cows you have at the top end. Identifying cows above 500k SCC/ml is often a good starting point. Next, find out which bacteria are causing the elevated SCC in these cows by milk sampling them; Milk sample collection packs are available from your Anexa clinic. We recommend collecting milk samples from at least 10 cows, this will give us a wide picture of what is occurring and allow us to make tailored recommendations for your farm PLUS we offer a discount when you get 10 or more sample done at one time. You can either RMT these high cows and sample the snotty quarters individually or you can do a pooled samples (2 strips from each quarter in the same pot). Talk to your vet about which option will suit what you are trying to acheive.

By collecting milk samples from the cows with the highest SCC we can identify:
  • Which bugs are causing the rise.
  • Whether the bacteria have come from the environment or the cow (contagious).
  • The effectiveness of your teat spraying.
From here, we can start to identify where the problem lies and suggest corrective actions to minimise the number of infected cows and therefore reduce the rise in cell count later in the season.

We can also use the first herd test to assess the effectiveness of the dry cow strategy. Cows that were high on herd tests last season that received dry cow therapy and are still high at first herd test, have not responded to the dry cow therapy i.e. have failed to cure. These animals are chronically infected and we are unlikely to cure the infection in the future. These chronic infections are most likely caused by contagious bugs, which they can then spread to other cows during milking. We can also assess whether the heifers (assume them to be uninfected before calving), are over represented in terms of increased SCC and if a change in management of these animals is needed to improve the situation next season.

If you would like some help to interpret the data from your first herd test, have a chat with your vet as getting your peak milk BTSCC as low as practical means more options later on!

Date Added: Thursday, 3rd September 2020