Slurry, Manure, and Bovine TB – it’s time to talk about poo!
- Badger Trust Staff Team
- Sep 13, 2024
- 9 min read
Updated: Apr 14
Ever wondered how cow poo could play a big role in the spread of bovine tuberculosis? It turns out it’s a pretty stinky situation!
While badgers often get the blame, it turns out the real mess lies in what cows leave behind — cow slurry and manure.
Our new article takes a closer look at how infected cows can spread bovine TB (bTB) bacteria through their dung, and how common farming practices, like spreading slurry on fields, could also be spreading the problem around our countryside.
Research shows that bacteria from bTB can survive in cow poo for months, lurking in slurry storage and even sticking around after it’s spread on fields. This poses a huge risk to other cattle and even wildlife.
But don’t worry, it’s not all doom and dung! We dive into simple ways farmers can tackle this issue, from cleaning machinery to treating slurry, all to help stop the spread of bTB. By addressing how we manage cow poo, we can protect our herds and our wildlife, and move away from badger culling.
Check out the full article for more on why tackling the slurry problem could be the key to stopping bTB in its tracks — without pointing fingers at our furry friends!
Slurry, Manure and Bovine TB
The BBC documentary ‘Brian May: The Badgers, The Farmers and Me’ released on Friday, 23rd August 2024, raised a key risk factor of bTB transmission, in that infected cows can shed Mycobacterium bovis in their dung, making transmission within herds highly likely via contact with infected faecal matter.
Research has shown that M. bovis persists in the faeces of infected cattle (Reuss et al, 1955; Neill et al., 1988; Maddock, 1936), particularly when the infection is advanced (Palmer et al., 2022).
Disease risk from slurry and manure
Because of the poor accuracy of bTB testing, farmers often struggle to identify which cows in their herd are actually infected. The documentary highlighted that a cow confirmed to have the disease could pass the SICCT skin test 20-30 times, allowing it to remain in the herd and potentially spread the infection to other animals.
As the disease progresses and undetected infected cows begin to shed bacteria in their dung, the risk of widespread infection within the herd increases significantly.
Even a single undetected case of a ‘supershedder’ can be catastrophic; one cow can produce up to 45 kilos of manure per day, becoming a ‘superspreader’, and dispersing bacteria through several pathways:
Direct defecation by infected cows into water sources, including water troughs and natural waterways, can lead to widespread contamination within and between herds.
Defecation on feed by infected cows can result in the ingestion of contaminated material by other animals, quickly spreading bTB within a herd.
Contact with faeces from an infected cow is a direct and rapid way for the disease to propagate through a herd, making biosecurity measures crucial for controlling bTB outbreaks.
It is common practice to use manure to fertilise crops or silage used to feed animals, or even directly onto pasture fields. In the documentary, the team tested the slurry on the farm, finding that 1 gram of slurry contained enough M. bovis to infect a cow.
Slurry does not undergo composting during storage and is therefore extremely unlikely to reach the high temperatures needed to kill pathogenic bacteria during storage (McCallan et al., 2014).
M. bovis bacteria can remain infectious for up to six months in stored slurry (Scanlon and Quinn, 2000), and survive on pasture for up to two months in the summer, and up to six months in the winter (Williams and Hoy, 1930).
When slurry from infected cows is spread on fields growing silage, the bacteria can contaminate the fodder, potentially infecting cows that consume it.
Spreading slurry directly on pasture fields exposes grazing cattle to the bacteria, increasing the risk of infection. This practice may also affect local wildlife, including badgers, that may forage in the fields.
While the risk of infection from manure is generally considered lower than from slurry, the possibility of TB transmission from improperly treated manure still exists. Solid manure undergoes a composting process, with temperatures of 50°C or higher being likely sufficient to kill the bacteria. However, composting conditions can be inconsistent, meaning that M. bovis can persist in parts of a manure stack.
How can the farming industry reduce or eliminate the risk of bTB transmission?
Implementing biosecurity and biocontainment measures focused on managing dung can significantly reduce the risk of disease transmission, including bovine tuberculosis, within a herd:
Keeping cow feed away from areas where cattle congregate helps prevent contamination from dung, reducing the likelihood of cows ingesting infected material.
Raising water troughs to a sufficient height ensures that cows cannot defecate in them, thus maintaining clean drinking water and minimising the spread of bTB and other pathogens.
Regular cleaning of cow sheds is essential in removing dung and other organic material, which can harbour bTB bacteria.
By maintaining a generally clean farm environment, the potential for disease transmission is greatly reduced, safeguarding the health of the herd.
To reduce or eliminate the risk of bTB disease transmission via slurry, several key practices can be implemented:
Avoiding the application of slurry on fields used for grazing or for growing animal feed significantly reduces the chances of cattle ingesting or coming into contact with contaminated material.
Storing slurry for at least six months before spreading allows time for the natural reduction of the bacterial load, making it less infectious.
Grazing on fields where slurry has been spread should be avoided for at least 60 days (Collins et al., 2000), as this is linked to higher disease risk (Griffin, 1993).
Treating slurry, for example by using chemical or heat treatments, can further diminish the presence of bTB bacteria before application (Olsen, 1985; Slana, 2011).
Injecting slurry or ploughing slurry into the ground immediately after spreading on cropland helps prevent aerosol transmission, reducing the likelihood of bacteria being inhaled by cattle or wildlife.
When using rented machinery for slurry spreading, equipment should be thoroughly sanitised before entry to the farm (Collins, 2000).
To reduce the risk of bTB transmission from manure, it is essential to ensure that solid manure is thoroughly composted before use:
Solid manure with low water content or high straw content should be left for at least 30 days before use to allow sufficient time for any bacteria to be neutralised.
Manure with a higher water content should be treated similarly to slurry and stored for longer periods, if possible, to ensure the bacteria are adequately managed and the risk of disease transmission is minimised.
These methods collectively contribute to lowering the risk of bTB spread and protecting both livestock and wildlife.
How much excrement do badgers produce?
Compared to cows, badgers produce very little excrement, around 300-600g (pers comms with local badger rescue groups), with studies estimating each badger only defecates once per night (Brown 1993).
Badgers are naturally clean animals, as shown through their meticulous behaviour towards their faeces. In addition, badgers will rarely, if ever, take food into their setts, and they are regularly observed grooming and cleaning out their bedding. Research on badger behaviour highlights their organised and hygienic habits (Kruuk, 1978), which starkly contrasts with cattle.
Badgers’ defecation habits, in particular, significantly reduce the risk of bovine tuberculosis (bTB) transmission when compared to cattle:
When badgers defecate, they generally dig small holes, known as dung pits, where they deposit their faeces.
These dung pits can either be isolated or grouped together in areas called latrines, which are used regularly by badger clans to mark territory boundaries or significant resources.
Badgers will faithfully stick to these sites to leave their faeces, even if the linear feature that marks a territory boundary is removed - if there is a straight line of dung pits through a field, you may find that there used to be a hedgerow or fence there!
This structured behaviour minimises the spread of bacteria and limits potential contamination, offering a clear distinction between the controlled habits of badgers and the less hygienic behaviours often seen in cattle, such as open defecation on feed or in water sources.
Is the risk of bTB spread from slurry and manure new information?
No. In the government-commissioned 2018 Godfray review of Bovine TB Strategy, the risk of slurry and manure management in bovine TB risk was made clear to DEFRA:
Specifically, the review highlights concerns that the potential for bTB transmission via slurry and manure spreading may have been previously underestimated, and underscores the importance of further research and mitigation strategies.
The review points out that the transmission risk of bTB is not only through direct contact and inhalation of bacteria, but also through feed or grazing areas contaminated by infected faeces or slurry.
The review notes that a significant percentage of dairy and livestock farmers rely on contractors for slurry spreading (Nye, 2018), which has been associated with increased bTB risk, as seen in a 2013 Northern Ireland study (O’Hagan et al., 2013). The movement of slurry tankers between farms without sterilisation has been identified as a potential risk factor (Richards, 1972), and the review emphasised that “M. bovis can survive in stored slurry for up to 6 months” (Scanlon and Quinn 2000).
The review outlined recommendations for reducing transmission from slurry and manure, including injecting slurry directly into the soil and introducing mandatory cleansing of contractor machinery between farm visits.
The government has been aware of the significant challenges farmers face in regard to biosecurity and biocontainment, and the risk posed by improper management of manure and slurry, for a considerable amount of time (DEFRA, 2020). And yet, badgers continue to be culled in the name of preventing spreading a disease in which they play a negligible role.
Further information:
What you can do to take action for badgers
The fight to save badgers goes on.
As the intensive badger slaughter begins again across England, badgers need your help.
Take action now!
Please get involved and show your support for badgers. Whatever you do could make a real difference in their lives.
Write to your MP
Email your newly elected MP about the cull and why you want them to represent your views and stop the cull now.
Make an appointment with your MP
Arrange a meeting with your MP in your constituency. Tell them you're advocating for an immediate end to the cruel badger killing. Ask them what they will do to help.
You can telephone or write to your MP to ask for a face-to-face appointment locally at their constituency surgery.
Telephone: Call the House of Commons on 020 7219 3000 and ask to be connected to your MP’s office.
Letter or email: Find your MP's contact details here.
MPs will generally only act on behalf of their constituents, so please check you are contacting the MP who represents your constituency.
It’s time for the new government to do the right thing for badgers, for farmers, for nature and #endthecull
The documentary ‘Brian May: The Badgers, the Farmers and Me’ is available to watch now via BBC iPlayer.
References
Brown, J. A. (1993). Transmission of bovine tuberculosis (Mycobacterium bovis) from badgers (Meles meles) to cattle (Doctoral dissertation).
Collins, J.D., 2000. Tuberculosis in cattle: reducing the risk of herd exposure. Cattle Practice, 5: 35–39
DEFRA, 2020. Next steps for the strategy for achieving bovine tuberculosis free status for England The government’s response to the strategy review, 2018. Available from: https://assets.publishing.service.gov.uk/media/5e60ad0de90e077e3d2678d2/bovine-tb-strategy-review-government-response.pdf
Griffin, J.M., Hahesy, T., Lynch, K., Salman, M.D., McCarthy, J. & Hurley, T. (1993). The association of cattle husbandry practices, environmental factors and farmer characteristics with the occurrence of chronic bovine tuberculosis in dairy herds in the Republic of Ireland. Preventive Veterinary Medicine 17, 145-160
Hutchings, M.R., Service, K.M. & Harris, S. Defecation and urination patterns of badgersMeles meles at low density in south west England. Acta Theriol 46, 87–96 (2001). https://doi.org/10.1007/BF03192420
Kruuk, H., 1989. The social badger: ecology and behaviour of a group-living carnivore (Meles meles). Oxford University Press, Oxford.
Kruuk, H., 1978. Foraging and spatial organisation of the European badger Meles meles L.- Behavioural Ecology & Socio-biology 4: 75-89
Maddock, E.C.G., 1936. Experiments on the infectivity for healthy calves of bovine tubercule bacilli, discharged in dung upon pastures. Journal of Hygiene, 36: 594–601
McCallan, L., McNair, J., Skuce, R. andBranch, B.A., 2014. A review of the potential role of cattle slurry in the spread of bovine tuberculosis. Agri-food and Biosciences Institute, Northern Ireland. Available from: https://www.daera-ni.gov.uk/sites/default/files/publications/dard/tb-slurry-lit-review.pdf
Neill, S.D., Hanna, J., O'Brien, J.J. and McCracken, R.M., 1988. Excretion of Mycobacterium bovis by experimentally infected cattle. The Veterinary Record, 340,::433–3343
Nye, C. (2018). https://ore.exeter.ac.uk/repository/handle/10871/33119
O’Hagan, M.J.H., Matthews, D.I., Laird, C. & McDowell, S.W.J. (2013) Bovine Tuberculosis Study, County Down, Northern Ireland 2010-2011, Department of Agriculture, Environment and Rural Affairs.
Olsen, J.E., Jørgensen, J.B. and Nansen, P., 1985. On the reduction of Mycobacterium paratuberculosis in bovine slurry subjected to batch mesophilic or thermophilic anaerobic digestion. Agricultural Wastes, 13(4), pp.273-280
Palmer, S., Williams, G.A., Brady, C., Ryan, E., Malczewska, K., Bull, T.J., Hogarth, P.J. and Sawyer, J., 2022. Assessment of the frequency of Mycobacterium bovis shedding in the faeces of naturally and experimentally TB infected cattle. Journal of applied microbiology, 133(3): 1832-1842.
Reuss, U., 1955. The occurrence of tubercle bacilli in the faeces of tuberculin-positive cattle and its significance in pasture hygiene. Die Rindertuberkulose, 4: 53–58
Richards, R. (1972). Inquiry into Bovine Tuberculosis in West Cornwall. MAFF, London; cited in McCallan, L. McNair, J and Skuce, R. (2014) A Review of the Potential Role of Cattle Slurry in the Spread of Bovine Tuberculosis, Agri-food and Biosciences Institute, Belfast. https://www.daerani.gov.uk/sites/default/files/publications/dard/tb-slurry-lit-review.pdf
Robertson, A. 2020. TB knowledge exchange. Available from: https://www. tbknowledgeexchange.co.uk/
Scanlon, M.P. & Quinn, P.J. (2000). The survival of Mycobacterium bovis in sterilised cattle slurry and its relevance to the persistence of this pathogen in the environment. Irish Veterinary Journal 53 (8), 412-415
Slana, I., Pribylova, R., Kralova, A. and Pavlik, I., 2011. Persistence of Mycobacterium avium subsp. paratuberculosis at a farm-scale biogas plant supplied with manure from paratuberculosis-affected dairy cattle. Applied and Environmental Microbiology, 77(9), pp.3115-3119.
Williams, R.S. & Hoy, W.A. (1930). The viability of B. Tuberculosis (bovinus) on pasture land, in stored faeces and in liquid manure. Journal of Hygiene 30, 413-419
Williams, R.S. & Hoy, W.A. (1930). The viability of B. Tuberculosis (bovinus) on pasture land, in stored faeces and in liquid manure. Journal of Hygiene 30, 413-419
