Marshland was associated with an increased risk of bTB, possible as a secondary effect of infection with liver fluke.

Practices such as larger herd size linked to higher risk of disease

New research by the University of Exeter has concluded that intensive farming practices, such as the use of silage and larger herd size, are linked to a higher risk of bovine TB.

The study, published in the journal Biological Letters, looked at data from 503 farms which have suffered a TB breakdown, alongside 808 control farms in areas of high TB risk.

The researchers found that herds with over 150 cattle were 50 per cent more likely to suffer a TB outbreak than those with less cattle.

Patterns of crop production were also important, with the risks increasing with practices linked with higher productivity systems. For every 10 hectares of maize - a favourite food of badgers - the risk increased by 20 per cent.

Dr Fiona Mathews,who led the study, said: “TB is absolutely devastating for farming, and it’s essential that workable solutions are found. In the worst hit areas, farms are frequently affected over and over again with crippling consequences. If lower intensity production means better animal health, it offers a sustainable long-term strategy in high risk areas.”

The study also found that the feeding of silage seemed to double the risk of bTB in both beef and dairy systems.

Landscape features such as woodland, marshes and hedgerow also had a major impact. The researchers observed that on farms with 50km of field boundaries, every additional 1km of hedgerow was linked with a 37 per cent reduction in risk - most likely due to less contamination of pasture by badger faeces and urine in hedgerow rich areas. 

Marshland was associated with an increased risk, possible as a secondary effect of infection with liver fluke - a disease which is linked to wet environments and interferes with the diagnosis of bTB in cattle.

Dr Mathews said: “To beat TB, we need to ensure our approach is robust and evidence-based. This is the first large-scale study to link a range of landscape-scale habitat features and farming practices with bTB. All of the effects we have found are additive, so changing several linked aspects of the farming system could potentially make a big difference.

"Farmers are already aware that biosecurity in the farmyard can help reduce the risk of bTB in cattle. We have now shown that wider environmental management is also important. By finding out more about these links, we hope that we can help eradicate this terrible disease.”