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The objective of this study was to evaluate the effects of ammoniated (AMB), roasted (ROB) and ammoniated- roasted (ARB) barley grain on milk yield, milk composition and rumen pH of lactating Holstein cows. To prepare processed barley,
barley grain was mixed with 4% urea solution with 100:75 ratio (barley:water) and
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ensiled for 60 days; barley was also roasted at tt5-t2OC (ROB) and then ammoniated
in the case of ARB. In this investigation twelve maltiparous Holstein cows in early lactation (52:t to DIM) with similar body conditions were assigned to four rations in a balanced change over design. The rations (63% concentrate, 37% alfalfa) were used as total mixed ration. The cows were fed rations contained 37% barley (ration 1), 37% AMB (ration 2), 37% ROM (ration 3) and 37% ARB ad libitum, for three periods (28 days/period) with 7 days interval. The rations were similar, as far as, ingredients, ingredients percentage chemical, composition and energy were concerned. Average daily milk yield (4% FMC) were 20.92, 23.10, 24.12 and 24.15 kg for the cows were fed ration 1,2,3 and 4, respectively. Milk fat percentages were 2.20, 3.30, 3.28 and 3.55 ; and protein percentages, 3.11, 3.30, 2.26 and 3.06, for ration 1 through 4, respectively. Average, of milk total solid percentage for ration 2 (12.4), and 4(12.07) were higher than ration 1 (11.6) and 3(11.90), the difference between these two groups was significant (P<5%). Dry matter intake for one kg milk yield (4% FCM) was 1.11, 1.04 , 1.03 and 1.00 kg for ration 1 through 4, respectively. The rumen pH of the cows was receviedration 1 was the lowest (6.02) while those fed ration 4 was the highest (6.43), the difference significant (P<5%).Fecal pH of the cows fed ration 1,2,3 or 4 were 6.12, 6.13, and 6.20 respectively with no significant differences. On the basis of these data, we can conclude that by ammoniating and/or roasting barley grain, it is possible to increase percentage of milk fat, milk yield and reducing the incidence of rumen acidosis in milking cows.