The Randomised Badger Culling Trial, or RBCT, is a large-scale field trial that was set up to quantify the impact of culling badgers on incidence of TB in cattle, and to determine the effectiveness of strategies to reduce the risk of a TB cattle herd breakdown.
The RBCT represents nearly ten years of work (1998-2007) and nearly £50 million of taxpayers' money. It was started after the Krebs Review on Bovine TB in Cattle and Badgers which reported in 1997. It concluded that despite there being 'compelling' evidence that badgers were involved in transmitting infection to cattle, the development of a control policy was made difficult because the effectiveness of badger culling could not be quantified with the data available.
It therefore recommended that a large-scale field trial - the Randomised Badger Culling Trial, or RBCT - be set up to quantify the impact of culling badgers on incidence of TB in cattle, and to determine the effectiveness of strategies to reduce the risk of a TB cattle herd breakdown.
The results of this robust experimental trial are fully published and peer-reviewed and represent the most substantial and coherent evidence base for the evaluation of badger culling. However, while the design of this experiment was exemplary, some have questioned how effectively it was carried out - in particular, all culling operations were suspended for a year in 2001 because of the Foot and Mouth Disease outbreak - and have raised doubts about the validity of the results on this basis.
How did it work?
The trial was conducted in thirty 100km2 areas of South West and central England, each located in a high-risk area for cattle TB.
The 30 areas were grouped into ten sets of three, each called a triplet.
Within each triplet, one area was subjected to repeated (approximately annual) culling across all accessible/consent land (proactive culling). In another area the badgers were culled on a single occasion locally, on and near farmland where recent outbreaks of TB had occurred in cattle (reactive culling).
The remaining area received no culling (survey only) and acted as an experimental control with which the culling areas could be compared. Participating farmers were aware of the treatment being applied to their area (i.e. they were not blinded).
Results showed that from one year after the last proactive cull to 25 February 2011, incidence of confirmed breakdowns in proactive culling areas was 16% lower than in survey-only areas.