Eight multiparous (n = 2) early lactating Holstein cows were used in a 4 × 4 Latin square design to determine effects of different levels of guar meal on the performance of dairy cows. Treatments were including 4 levels of guar meal: T1) 0, T2) 4, T3) 8, T4) 12% of DM that substitute to soybean meal. Treatments effect on DMI (kg/d) were not significant (P > 0.05). Milk yield were increased for cows fed T2 compared with other treatments (43.392, 46.480, 44.100 and 43.080, respectively) (P < 0.05). Milk fat (%) was increased for T2 compared with T3 and T4 (P < 0.05), but had no difference between T1 and T2 (P > 0.05). Milk protein was not influenced by treatments (P > 0.05). Treatments effect on pH were significant (P < 0.05), cows fed T2 had lower pH than control (6.58 vs. 6.36). It was concluded that substitution 4% of soybean meal with guar meal had the best effect on performance. Table 1. Effects of different levels of guar meal on DMI, rumen pH, milk yield and composition T1 T2 T3 T4 SE Pvalue DMI (kg/d) 26.805 26.975 26.717 26.968 0.445 >0.05 Milk yield (kg/d) 43.392b 46.480a44.100b 43.080b 0.806 <0.05 Milk Fat (%) 3.717ab 4.101a 3.380b 3.424b 0.162 <0.05 Milk protein (%) 2.803 2.592 2.688 2.715 0.110 >0.05 rumen pH 6.588a 6.367b 6.381ab 6.406ab 0.070 <0.05 T1, T2, T3 and T4= levels of guar meal (0, 4, 8 and 12% of DM respectively). SE= standard error of means.

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