The study evaluated the protein and carbohydrate fraction, dry matter (DM) and crude protein (CP) effective rumen degradability (ED), DM and CP in vitro ruminal digestibility (RDIV), rumen-undegradable protein (RUDP) in vitro intestinal digestion (IDIV) and amino-acid (AA) and fatty acid (FA) profile of the wet brewer’s grain (WBG), and fermented brewer’s grain (FBG). FBG was obtained from WBG fermentation. The DM and CP ED of WBG and FBG were determined in three Holstein steers with ruminal cannula. The IDIV of RUDP was obtained by the three-stage method. The values obtained for DM and CP ED were submitted to variance analysis, in a randomized design. The A fraction of WBG CP was 7.9%, and for FBG 13.1% of CP. The CP RD in a rate of 5% h-1 did not differ (p > 0.05) between WBG and FBG. The crude protein RDIV of FBG was 8.7% and IDIV of RUDP of WBG and FBG were of 70.5% and 72.5%, respectively. The AA and FA profile of WBG and FBG were similar. The anaerobic fermentation process did not change the nutritional characteristics of the WBG.