Determining Risk and Status

• While it is calculated that 1/3rd of dairy herds do not have Johne’s Disease present on farm, a robust plan to keep the disease out – or manage the infection if present needs to be worked up with each farm’s own vet.

• If your risks of Johne’s Disease are high, it is important that you reduce them by adopting an effective control programme and monitor carefully for infection within your herd

• Testing will help determine your herd’s Johne’s Disease status’ as part of your control programme

 

Updated Johne's picJohne’s infection is mainly caused by calves ingesting faeces from contaminated bedding, udders, teats or on dirty buckets of colostrum or milk. Much less commonly the disease can be acquired in the womb or later in life.


It should be noted that Johne’s disease testing using milk and blood samples should not be carried out until at least 45 days after a TB test (for further information see Resources page).

Risk based (quarterly testing)
Suitable for herds of moderate to high prevalence who are not able to dedicate the resources or have the facilities required for Improved Farm Management on all cows calving. Frequent testing allows the creation of a low risk group (green cows, typically 90% of the herd) which are managed normally and a high risk group (red and amber cows) of cows which are separated at drying off into a dedicated segregation area to prevent contamination of green cows and green cow areas. Test results are also used to inform breeding and culling decisions.
This programme is especially suited to herds which undertake milk recording as the Johne’s testing can be carried out on the milk recording samples. The overall cost of the program may be offset by savings on labour and higher cull prices for cows identified early in the infection cycle.
Single test (Pre Dry off)
This is a less rigorous testing programme, with just a single test performed before drying off. This result is used to segregate test positive cows at drying off into a dedicated area away from the low risk cows.
The single test will not be as sensitive as repeated testing and as such not all infectious animals may be identified allowing some to enter the calving area and spread the disease.
This option may be suitable for block calving herds with low prevalence which can test all of the animals in one session pre dry off. It is more challenging to ensure timely testing in a year round calving herd with cows going dry every month. Adequate resources are needed to ensure cows are sampled at the appropriate time.

Double test (Pre Dry off and Pre Breeding)
This increased testing provides greater sensitivity than the single test and also provides a test result pre breeding to allow breeding decisions to be made. This option may be suitable for block calving herds with low to medium prevalence.