The authors are grateful to Ramon Costa and the
team of the SGCE (Servei de Granges i Camps Experimentals,
Bellaterra, Spain) of the UAB for the care
of the animals, and to Nic Aldam for reviewing the
manuscript. This study was partially funded by the
Ministerio de Ciencia y Tecnologı´a of Spain (CICYT
project AGL2001-2617). M. Amine Bouattour was
granted a scholarship from the AECI (Agencia Espan˜
ola de Cooperacio´n Internacional, Spain).