A DEFRA pilot study on the cost benefit analysis of badger control found that increasing badger culling rates above 80% had little effect on reducing the number of cattle herd breakdowns.
Only a small benefit was observed when the culling rate was increased from 60% to 80%.
However, the study concluded that “the results are not robust enough to provide evidence to support or reject methods of culling badgers”.
The model used in the project aimed to estimate the overall effect on bovine TB in cattle of two different badger control strategies – trapping followed by shooting, and gassing.
The report also acknowledged that culling badgers over a large area with one campaign might be more effective than culling small areas with repeated campaigns in terms of reducing cattle herd breakdowns, but not more cost-effective.
Culling badgers by trapping and shooting was more expensive than gassing, nevertheless, the overall economic benefit of gassing would not be realised for more than 10 years.
The time constraints of the project meant that the data used to assess the effects of cattle movement were least reliable.
An early assessment suggested that between 26% and 85% of cattle herd breakdowns were not linked with new cattle being moved on to farms and thus might be associated with other reasons, eg badgers.
The pilot was a short preliminary study involving significant levels of uncertainty.
DEFRA has funded an additional two-year project which will seek to build on the findings of the preliminary study, to refine the assumptions used and to validate the findings with independent models and existing data.