High producing dairy cows may need to organic chromium source (Cr) and yeast culture (YC) as supplements due to the high grain intake daily. In this study the effect of Cr and YC inclusion into the dairy cow’s rations on performance, nutrient digestibility, ruminal fermentation profiles, feeding behaviors and serum blood metabolites were investigated. In total, twelve high producing Holestein dairy cows with days in milk (55.5 ± 4.2 d; mean ± SD) and average milk production (45.6 ± 3.5) in third parity were selected and randomly allocated into the replicated 3 × 3 latin square design with 28 days periods. Cows fed with a basal diet or diets supplemented with Cr and YC which included on top dress. Therefore, experimental diets were control, Cr and YC. Each period consisted of 21 days adaptation and 7 days data collection. Results showed that, cows fed diets contained YC and Cr had greater DMI, OMI, CPI, NDFI and ADFI compared with cows fed control diet (P<0.05). Cows fed diet supplemented with YC had greater body weight and body weight gain compared to those fed with control diets (P < 0.05) while cows fed diet supplemented with Cr were intermediates. Milk production and composition and milk to dry matter ratio were similar among cows fed different dietary treatments (P > 0.05). Ruminal pH, NH3, total VFA and individual VFA concentration were not affected by dietary treatments. Feeding behaviors including rumination, water intake, and resting time during 24 h were similar among cows fed different dietary treatments. Cows fed diets supplemented with YC spent lesser time for total feed intake compared with other cows (P=0.1). Cows fed YC and Cr supplemented diet had lesser time for intake of each kg of DMI and NDFI (P = 0.01) compared with control group cows. Cows fed different experimental diets had similar serum parameters for carbohydrates, proteins and energy metabolism, liver function and total antioxidant capacity of the body. In conclusion, under condition of co
