ABSTRACT: Feeding animals with either concentrates or alfalfa grazing has been proven to reduce the oxidative process that occurs in meat products. Indoor-kept lambs were fed a standard concentrate (n=7, C) before slaughtering all animals at 22–24 kg of live weight. Simultaneously, 7 unweaned lambs grazed in alfalfa paddocks (ALF) with their dams. Global transcriptomic data of liver with the Affymetrix® Ovine Gene 1.1 microarray was used. When ALF group was compared with C group, were identified 96 genes differentially expressed. Among these genes 92 were down- regulated and 4 were up- regulated. The clusters corresponding to gene expression profiles from treatments were clearly separated from each other. These differentially expressed genes were selected for a functional analysis by using DAVID. Three major gene clusters associated with “sterol biosynthesis (EBP, MVD, HMGCR, CYP51A1, HMGCS1, NR0B2, C14ORF1, FDFT1, SQLE, DHCR7, SC5DL, DHCR24, NSDHL) , “lipid biosynthetic process (ACACA, CYP51A1, FADS1, FADS2, SCD y SC5DL)”, “cholesterol metabolic process (EBP, MVD, HMGCR, CYP51A1, SQLE, DHCR7, HMGCS1, NR0B2, DHCR24, FDFT1, NSDHL)” were found.