1. CIRAD, UMR CMAEE, F-34398 Montpellier, France; INRA, UMR 1309 CMAEE, F-34398 Montpellier, France
2. Animal Production Unit, FAO/IAEA Agriculture and Biotechnology Laboratory IAEA Laboratories A-2444 Seibersdorf, Austria
3. The Pirbright Institute, Pirbright, Surrey, United Kingdom