What is Johnes?
Johnes disease is a chronic disease which affects all ruminants by reducing the lining of the intestines’ ability to absorb fluid and nutrients. If your cows occasionally show clinical signs of scours, cell counts go up and milk drops, it is possible that a proportion of the herd is infected. Having Johnes will increase their susceptibility to other diseases.
Johnes is caused by MAP (Mycobacterium Avium subspecies Paratuberculosis), which can be shed in the faeces, colostrum, or milk of infected animals. Around 80% of infections occur in the first month of life, with the biggest risk period thought to be the first few days after calving. Resistance to new infection increases as the animal gets older, and new infections in adult animals are relatively rare. The main route of infection for calves is the ingestion of faeces contaminated with MAP. Although direct ingestion of faeces does occur, calves are more commonly infected through ingestion of muck from contaminated bedding, udders, teats or buckets.
Are you spreading more than slurry?
Both Johnes and TB can survive in slurry and can be a source of transmission of these diseases that most farmers wouldn’t think to consider. The survival time in slurry for each pathogen varies. The TB bacteria can survive for up to 6 months in slurry whereas the Johnes disease bacteria (MAP) can survive for up to a year in slurry.
Infected cattle can shed the pathogens in their dung, which is then mixed and stored with non-contaminated slurry or FYM. When this is spread across the grassland, there is a risk that it could be transmitted to cattle, especially grazing animals. Youngstock are the most susceptible to infection, therefore minimising the grazing of youngstock on land that was recently spread with slurry or manure is very important.
The pathogens can survive for extended time in both the grazing and silage. If silage is made well with a good fermentation it can reduce the survival rate of both the TB and Johnes pathogens to a month. Whereas on the grazing platform, it can last for a longer period of up to a year.
Therefore try to manage your manure applications with TB and Johnes in mind by:
- Focus your slurry applications onto silage ground if at all possible – this will also help balance phosphate and potash offtakes from your silage and minimise your fertiliser spend.
- If you have to spread manure on grazing land, do it if you can in the autumn as the pathogens are less lively to survive a cold winter.
- Try not to spread manure on your youngstock grazing land in particular if at all possible as these are the most susceptible animals.
- If you do have to spread on your grazing block in the spring try to spread as soon as cows leave the paddock so that there is minimum leaf to contaminate, or better still if injection is an option consider this.
If you are importing slurry or manure from other farms, make sure you aware of the risks coming from those farms and check out their TB and Johnes status is like. Also to review manures coming from other pathogen carriers ie: Pigs.
