1. Royal (Dick) School of Veterinary Studies and the Roslin Institute; Division of Clinical Veterinary Sciences; University of Edinburgh; Easter Bush Veterinary Centre; Roslin Midlothian EH25 9RG UK
2. North Carolina State University; Department of Clinical Sciences; Raleigh NC 27607 USA
3. Biochemistry Laboratory; Langford Veterinary Services; Langford House Langford North Somerset BS40 5DU UK