Nine multiparous midlactation Holstein cows (131.44±9.32 DIM, 30.2±5.14 kg daily milk yield) were fed a total mixed ration supplemented with ground barley grain (control), or whole barley grain treated with sodium hydroxide (10%) and dried in different periods including: dried immediately (0h) or after 48h storage in plastic bags (48h). Sodium hydroxide was used at the level of 3.5% (DM). Each period lasted 3 week; experimental analyses were restricted to the last week of each period. Diets were formulated according to NRC 2001. Cows were housed in tie stalls and fed the TMR two times a day to allow 5 to 10% orts (as-fed basis), and dry matter intake (DMI) was recorded at the last week of each period. Data were analyzed as a 3 × 3 Latin square using the GLM procedure of SAS (2001). The model included effects of diet, period and cow. Least squares means are reported throughout and significance was declared at P < 0.05. Diets had no effects on DMI (21.49, 22.35 and 20.19 ± 0.67 kg/d for control, 0h and 48h respectively), CP intake (3.4, 3.55 and 3.41± 0.16 kg/d for control, 0h and 48h respectively), NDF intake (7.69, 8.25 and 7.32 kg/d for control, 0h and 48h respectively) but OM intake (20.52, 19.78 and 18.45 ±0.56 kg/d for control, 0h and 48h respectively) and ADF intake (5.24, 5.65 and 4.63 kg/d for control, 0h and 48h respectively) decreased in 48h diet. The digestibility of DM (67.66, 69.22 and 67.77±1.7% for control, 0h and 48h respectively), OM (68.66, 70.22 and 69.22±1.6% for control, 0h and 48h respectively), NDF (59.44, 60.66 and 58.33 ±2.4% for control, 0h and 48h respectively) and CP (68.44, 70.11 and 69.89±1.9% for control, 0h and 48h respectively) were similar between diets, but ADF digestibility (57, 64.77 and 51.44±3.5% for control, 0h and 48h respectively) decreased in 48h diet in comparison with 0h diet; however 0h diet had more NDF digestibility than control diet. The results of the current experiment reveals that chemical treatment of whole barley grain with sodium hydroxide for 48h had negative effects on ADF intake and digestibility

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