Herds of 150 cattle or more are 50% more likely to suffer a bovine TB outbreak than those with herds of 50 or fewer, new research has found.

The study by the University of Exeter found that intensive farming practices have been linked to higher risks of TB.

Patterns of crop production and feeding were also important, with the risks increasing with practices linked with higher productivity systems, it found.

For every 10ha of maize – a favourite food of the badgers that play a role in transmitting the disease – TB risk increased by 20%, the study found.

The feeding of silage was linked with a doubling of the risk in both dairy and beef systems.

Landscape features such as deciduous woodland, marshes and hedgerows were also important e.g. on farms with 50km of field boundaries, each extra 1km of hedgerow was linked with a 37% reduction in risk.

The study found that this is likely to be because there is less contamination of pasture by badger faeces and urine in hedgerow-rich areas.

Marshland was associated with increased risk, possibly as a secondary effect of infection with liver fluke – a disease linked with wet environments and which interferes with the diagnosis of bTB in cattle, the research found.

Dr Fiona Mathews, Associate Professor in Mammalian Biology, who led the study, said that 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.

“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 bovine TB.

“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 bovine TB in cattle,” she said.