1. Animal Nutrition and NIR Lab., Instituto Nacional de Investigacion Agropecuaria, INIA La Estanzuela, Ruta 50 - km 12, Colonia, Uruguay; United Fish Products Ltd. Tullos, Aberdeen AB12 3AY, Scotland, U.K.; Department of Agriculture, MacRobert Building, University of Aberdeen, Aberdeen AB12 5UA, Scotland, U.K.; and Scottish Agricultural College, Animal Biology Division, Ferguson Building, Craibstone State, Aberdeen AB21 9YA, Scotland, U.K.