Affiliation: | 1. University of Bristol Veterinary School, Langford BS40 5DU, UK;2. Soil Association, South Plaza, Marlborough Street, Bristol BS1 3NX, UK;3. Royal Society for the Prevention of Cruelty to Animals, Wilberforce Way, Southwater, Horsham, West Sussex RH13 9RS, UK;4. Swedish University of Agricultural Sciences, P.O. Box 7068, 750 07 Uppsala, Sweden |