By vet Anne Abbs
Anyone who has already done their health plan and Johnes declaration for 2026 will have noticed a change in the testing required for their Johnes plan.
In the past the test has been a (minimum) of a 30-cow targeted screen i.e. testing the cows most likely to be infected. Before showing any clinical disease, cattle infected with Johnes are more likely to suffer a range of symptoms and production losses, for example they are more likely to be infertile, have a high SCC or low yield and weight loss.
Targeting these cattle gives you a very good idea of whether there is any Johnes infection in the herd but doesn’t give you a handle on how many cows are infected or how severe that infection is.
The new measure of a minimum 60-cow random screen tracks that and helps inform your progress (or otherwise) through time.
For herds doing regular whole herd milk tests, tracking ATV can help indicate whether control measures are working. It is important for consistency to ensure that the testing is truly random and reflects cows at different stages of the production cycle. If the herd is milked in different cohorts e.g. high and low yielders; heifers and cows, samples should be taken out of all groups.
If the whole milking herd isn’t being sampled but you do milk record it is possible to get your milk recorder to calculate the ratio of cows needing sampling, which cow to start on and to take the appropriate samples. If you want to take the samples yourself then you need to agree a protocol in advance with the vet who will be signing your declaration.
It is possible to use blood samples to monitor progress for your Johnes declaration, but these are not comparable to milk samples and can’t be benchmarked. It is also important that the samples are random, similar to the milk samples and include cows in different stages of the production cycle e.g. sampling at drying off alone isn’t sufficient even if all the herd are included.
The UK national target set by Actionjohnesuk is to have herds at 5.5 or less by 2030.
Currently about 43% of herds have already achieved this but others have a long way to go yet. To put this into context, the national average was 10 in 2015 and had reduced to 6.6 by 2013. This indicates a lot of thought and effort by farmers and vets to reduce the spread of this insidious disease.
If you are one of the 43% that have achieved the target, well done but make sure you continue to work on control and get rid of J5 and priority cull cows to avoid the risk of them spoiling all your hard work.
For anyone nearer the start of the journey, discuss with your vet the most important actions you can take to reduce transmission and target those, it may be culling a few very high shedders or tweaks to calving hygiene that are required.