Johne’s disease (JD) is a bacterial disease of cattle for which there is no cure and is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP).
JD is often assumed to be associated with older animals in the herd at usually three to three to five-years-old where the cow develops a persistent, profuse diarrhoea and will have significant weight loss.
These clinical cases more often than not are not present on a frequent basis, as generally animals are culled because of reduced performance, infertility or other disease.
So before farmers even realise they have an infected animal, the animal is culled from the herd, meaning that the economic and welfare burden that the disease causes is much more insidious than directly through clinical cases.
The impacts of JD in your herd are as follows:
- Reduced milk production;
- Premature culling leading to increased cost of unnecessary stock replacement;
- Lower value cull animals;
- Increased levels of lameness;
- Lower feed conversion efficiencies leading to increased feed costs;
- Negative effects on herd fertility;
- Higher cell counts;
- Increased veterinary costs and associated increase in antimicrobial usage.
As herd infection increases, the losses associated with these areas will increase which leads to greater economic loss and welfare impacts on farms.
Economic losses in herds that keep JD prevalence low are negligible, which show the importance of having knowledge about your herd’s JD status and having a control programme in place for your farm.
Johne’s disease cost
The economic loss associated with decreased milk production had been studied and has compared Ireland to other countries (Rasmussen et al. 2021).
It concluded that internationally approximately 1% of gross milk revenue which is the equivalent to €31/cow is lost annually in MAP infected dairy herds.
These losses are primarily driven by reduced production and being higher in regions charactarised by above average milk price and production per cow.
It was estimated in the study, how much JD was costing the Irish dairy industry, using two sets of assumptions which was calculated to vary from €11.24 million to €23.85 million per year, depending on assumptions used.
This information simply shows that if we control the level of JD infection to low levels in the national herd it will have a knock on positive economic effect on the industry as a whole.
Not only that, but this beneficial economic effect from implementing control programmes will also contribute to better welfare conditions for stock.