The objective of this study was to determine the effect of diets containing different types of non-fiber carbohydrates [sucrose (Su), starch (St) or equal mixture of Su and St (Su+St)] on ruminal peptide-N concentration of Holstein steers. Four ruminally fistulated steers (body weight = 280 ± 15 kg) were assigned to a 4 × 4 Latin square with 28 d periods. The basal diet contained alfalfa hay, barley grain, soybean meal and sugar beet pulp (400, 290, 190 and 50 g/kg respectively). The non-fiber carbohydrates were added to the basal diet at the rate of 70 g/kg DM. Diets were offered at 2.5 times of the maintenance requirements (7 kg DM/day). Animals were fed twice daily at 08:30 and 16:30. Samples of rumen contents were taken, by suction, at 0.0, 2, 4 and 6 h after the morning feed. Ruminal fluid was prepared for peptide-N analysis using sulfate-tungstate precipitation method. Tungstate acid-precipitate nitrogen was assayed by a standard macro-Kjeldahl procedure. Data were analyzed using mixed procedure of SAS (2003) for repeated measures. Results of the present experiment indicate that peptide-N concentration tended to be lower when steers were fed Su, St and Su+St than BD (P = 0.09). Mean Peptide-N concentrations of the sampling times were BD = 2.1, Su = 1.7, St = 1.4 and Su+St = 1.5 mg/dL. Therefore, it might be concluded that the nitrogen metabolism in the rumen is affected by the

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