Soybean and canola meals are major protein sources in dairy cows diets. In this study, the effect of grains and canola meal processing on reducing, replacement of canola meal instead of soybean meal were studiet on the performance of high-producing cows. In in vitro studies, heat treatment were chosen at 130° C for 30 minutes. In in vivo study, eight lactating cows (second parity) 42±2 days in milk, 46 ± 3 kg of milk production and 650 ± 20 BW were used. Four treatments were included: 1) Soybean meal based diet containing 16.6% crude protein, 2) untreated canola meal based diet with 17.7% crude protein, 3) treated canola meal based diet with dietary 16.5% CP and 4) treated canola meal and steam flacked grain based diet with 15.3% CP. Metabolizable protein were similar among diet. The results showed that dry matter intake was not affected by treatments. Protein intake was greast in untreated canola meal diet and lowest in treated canola meal diet (P 0.05). Milk yield in soybean meal, canola meal, untreated canola meal and treated canola and steam flacked grain were 43.8, 41.4, 42.3 and 43.0 kg, respectively which showed no statistical differences (P 0.05). Milk composition were not effected by different treatments (P 0.05). Dry matter digestibility and CP intake in cows fed diet based soybean meal, were more than diet based canola meals. Blood metabolites such as urea, glucose, creatinine and also chewing behavior were not affected by treatments but cowes fed soybean meal and treated canola meal spent more time for eating than cows (P 0.05). The results showed that we can reduce CP content of diets with treated grain and protein sources, without negative effects on cow performance.Cows fed treated canola meal produced similar milk as cows fed soybean meal. Keywords : Dairy cows, soybean meal, canola meal, processing, crude protein
