Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs how many herds are participating ingamma-interferon testing. [158388]Mr. Bradshaw: By the end of February 2004, 88 herds had been recruited to the gamma-interferon field trial.In addition, between 1 January 2003 and 29 February 2004, ad-hoc gamma-interferon tests were approved in 19 herds thatdid not qualify for the field trial. Formal instructions were issued to the State Veterinary Service in November 2003, which providefor the use of the gamma-interferon test in the following circumstances: to aid decision making in relation to whole or partial herdslaughter in severe TB breakdowns1; as a parallel test for non-reactor cattle in ongoing, confirmed TB incidents with a chronic TBproblem, but which do not qualify for the field trial1; or as a serial test, to resolve skin test reactors or inconclusive reactorsin prolonged unconfirmed TB incidents within low TB prevalence areas where there is a suspicion of non-specific reactivity to theskin test2.1 gamma-interferon used to enhance overall sensitivity of testing, 2 gamma-interferon complements skin test to achieve betterspecificity.