As the breeding season approaches on farms it’s time to start selecting cows for culling.
There are a number of reasons why cows are selected for culling from a herd including: Production, fertility, health, lameness and many more.
Culling
The culling of cows takes place on every dairy farm and as previously stated, there are a number of reason why.
Culling is an important part of dairy farming to remove ‘problem cows‘ from the herd.
This allows for space to be created for young, high-genetic merit animals to come into the herd.
When selecting cows for culling, disease risk is something that farmers should consider. Johne’s Disease is something in particular, that farmers should look at when selecting cows.
Johne’s Disease
Mycobacterium avium subspecies paratuberculosis (MAP) can easily be spread from one animal to another, particularly if you feed a calf colostrum from an infected cow.
The Irish Johne’s Control Programme (IJCP), operated by Animal Health Ireland (AHI), is developing a long-term programme to control Johne’s Disease within the Irish cattle industry.
Although animals become infected at a young age, symptoms are often not expressed until later in life.
By the time it is detected is it possible that the disease has been spread to other animals within the herd.
Regular screening of your herd is the best way to detect the presence of MAP bacteria within your herd.
The three main ways of testing for the disease are through:
- Blood testing;
- Individual milk sampling; or
- Individual faecal sampling.
It is recommend that you wait at least three months after bovine tuberculosis (TB) testing before testing for Johne’s Disease.
Johne’s Disease has been present in Ireland since at least 1956. Although a closed herd may have been operated for many years, it is possible that the disease might already be on your farm.
Risk
AHI have developed a list which farms can use when determining if cows should be culled due to their Johne’s risk.
In descending order of risk:
- Clinical cases (signs of severe wasting in condition and diarrhoea, bottle-jaw, eventual death, usually bright and alert until the terminal stages);
- Positive result to culture or PCR test on a dung sample;
- Positive or inconclusive result to ELISA test on a blood or milk sample;
- Calves, especially the most recent calf from high-risk cows – earlier calves are lower risk as infection in the dam will not have progressed as far towards spreading to the calf;
- Animals calved and raised in same calf cohort as high-risk animals;
- Introduced animals from a known-infected source herd;
- Introduced animals from same source herd as animals identified as high-risk;
- Introduced animals from source herds of unknown status and likely uncontrolled risk management.