Effect of feeding treated corn stover and modified wet distillers grains with solubles to replace corn on ruminal pH change over time in Exp. 2. Steers were fed 1 of 5 dietary treatments: 1) 55% corn and 5% untreated ground CS (CON, diamonds), 2) CS treated with 5% CaO (DM basis) and stored in an Ag-Bag (BGCS, squares; Ag-Bag, A. Miller-St. Nazianz Inc., St. Nazianz, WI), 3) CS treated with 5% CaO (DM basis) and extruded (5 EXCS, triangles), 4) CS treated with 4% CaO and1% NaOH (DM basis) and extruded (4,1 EXCS, circles), or 5) CS treated with 3% CaO and 2% NaOH (DM basis) and extruded (3,2 EXCS, crosses). There was a time × treatment interaction (P < 0.01) on ruminal pH. There was a main effect of treatment (P = 0.02) on ruminal pH. The error bars reflect the SEM associated with the interaction of treatment × time (SEM = 0.10).