To study the effect of two barley processing methods on milk production and composition, eight Holestein cows (Multiparous cows) were used in 85 ± 25 d in milk. Experimental diets were differed in respect to processing methods (two methods) and barley level (tow levels). The treatment consists of 1) 35% ground barley (mean particle size about 1mm), 2) 30% ground barley, 3) 35% steam-rolled barley (PI about 70%), and 4) 30% steam-rolled barley. The processing index (PI) is a measure of weight of a given volume of barley after rolling as percentage of the weight of whole barley. This experiment was conducted as duplicated 4 × 4 Latin square design (21-d periods). Forage to concentrate ratio was 38:62. the diets were offered as total mixed ration twice a day. Milk yield was higher for cow received steam-rolled barley than ground barley (P 0.05), more over, observed response was increased due to processing by increasing the level of barley. Fat corrected milk and energy corrected milk were higher in steam-rolled barley diets (P 0.05), It has similar trend as milk production with the increased level of barley. Digestibility of DM and OM were trend to increase in steam-rolled barley. Fat and protein percentage, DM and OM Intake, NDF and ADF digestibility, ruminal pH and chewing activity were not affected by barley processing and barley level (P 0.05). The result is represented that replacement of grinding method by steam-rolling method increment in milk production, FCM and ECM, this maybe due to Numerical increase in DM or OM digestibility. According to higher difference between tow processing method with increasing the level of barley, it was conducted steam-rolled processing increased dairy cow performance specially in higher level of barley.
