In dry and semiarid regions, because of low pasture availability, ruminant diets are based on concentrates. The objective of the present experiment was to investigate the effect of diets providing different concentrate to alfalfa hay ratios on blood metabolites in Holstein steers. Four Holstein steers with initial body weight of 300±15 kg tted with ruminal Fistulae were used in a 4×4 Latin square design (28 days of each period). Animals were fed 7 kg of DM of diets differing in concentrate [155 g CP kg-1 of DM; consisted of maize, barley, soybean meal, sugar beet pulp, wheat bran, cottonseed meal, CaCo3, mineral and vitamin premix, salt (30, 34, 8, 5, 10, 12, 0.3, 0.5, and 0.2 g/100g DM; respectively)] to alfalfa hay ratios as 60:40 (C60:L40), 70:30 (C70:L30), 80:20 (C80:L20) and 90:10 (C90:L10). Steers fed the experimental diets as total mixed ration twice daily at 0800 and 2000 h. At day 24 of the each experimental period, blood samples were taken from jugular vein before the morning feeding, 2, 4 and 6 h post feeding. Serum samples were measured for glucose and urea N by Spectrophotometer (CE 1021, England). Data were analyzed using the GLM procedure of SAS and the means compared by the Duncan test (P <0.05). Blood glucose was similar among diets but blood urea N was affected by treatments. The results of this study indicated that the blood glucose values were not signicantly inuenced by the concentrate to alfalfa hay ratios but urea N values were inuenced signicantly.

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