The proper processing of cereal grains may reduce the need for escape proteins in dairy cows diets due to the increased microbial protein synthesis. Two experiments were conducted to investigate the interactions of RDP to RUP ratios with corn processing method and sources of RUP on production performance of high-producing Holstein dairy cows. In experiment 1, the effects of rumen-degradable protein to rumen-undegradable protein ratio (65:35 vs. 60:40; RDP: RUP) and corn processing (ground vs. steam-flaked) on the performance were evaluated using 12 Holstein dairy cows. In experiment 2, eight lactating cows were used 4×4 Latin square design that included 4 treatments. Treatments 1 to 4 in the second experiment consisted of diet containing xylose treated Soybean meal, fish meal, meat meal, and the mixed of fish and meat meal as RUP sources, respectively. Higher percentage of RDP improved milk production, and thereby feed efficiency. Compared with ground corn, steam flaking decreased dry matter intake, 4% fat corrected milk, and milk fat percentage. The result of second experiment showed no significant effect of RUP sources on DMI, milk yield and composition in high- producing Holstein dairy cows with the conditions of the present study. No significant interactions of main treatment effects occurred for lactation performance data, but on the grounds of their lower costs, Increasing RDP concentration from 10 to 10.8% and ground corn, also the use of meat meal as RUP source can be effective feeding strategies and may be more economical for high producing dairy cows fed high concentrate diets. Keywords : Rumen undegradable protein, Corn Processing, high producing Holstein dairy cow
