1. UMR1079 SENAH, INRA, F-35590 Saint-Gilles, France, Departamento de Produccion Animal, Universidad Nacional de Colombia, Carrera 32 Chapinero, Palmira (Valle), Colombia, Prairie Swine Centre, 2105 Eighth Street East, Saskatoon, SK, S7H 5N9, Canada, Centro Internacional de Agricultura Tropical, AA 6713, Cali, Colombia, and Department of Nutritional Physiology Oskar Kellner, Forschungsinstitut für die Biologie landwirtschaftlicher Nutztiere, Wilhelm-Stahl Allee 2, 18196, Dummerstorf, Germany