Waste dates are all damaged dates containing core that don’t use for human consumption and have usability as a by-product. The goal of this study was to evaluate the effects of using alfalfa silage treated with different varieties of waste date on feed intake, nutrient digestibility, milk yield and composition of Holstein lactating dairy cows. Eight Holstein lactating dairy cows with days in milk 100 ± 4 d and average milk yield of 41 ± 1 kg were used. Treatment were 1) alfalfa silage without waste date (control), 2) alfalfa silage containing 6% Brin waste date, 3) alfalfa silage containing 6% Ghybani waste date and 4) alfalfa silage containing 6% Amobahri waste date. Data were analyzed as 4 × 4 change over design by the MIXED procedure of SAS (P < 0.05). The dry matter intake in cows fed with control was significantly lower (P < 0.05) than other treatments (21.89, 23.41, 23.49 and 23.85 kg in control and T2, T3 and T4, respectively). The apparent digestibility of dry matter, organic matter, crude protein, neutral detergent fiber and acid detergent fiber was not affected (P > 0.05) by dietary treatments. Milk yield in cows fed with all alfalfa silages treated with waste date were increased significantly (P < 0.05) than control diet (35.76, 37.69, 37.54 and 37.48 kg in control, T2, T3 and T4, respectively); however, 3.5% fat-corrected milk yield and energy-corrected milk yield were not affected (P > 0.05) among treatments. Percentage of milk components like fat, protein, lactose, nonfat solids and total solids were not affected (P > 0.05) by dietary treatments, but amount of milk lactose (kg) was significantly higher (P < 0.05) than control in cows fed with alfalfa silages treated with all different varieties of waste dates (1.68, 1.78, 1.75 and 1.79 kg/d in control, T2, T3 and T4, respectively). Rumen PH was significantly lower (P < 0.05) in cows fed with alfalfa silage treated with all varieties of waste dates. However, the ruminal ammonia nitrogen concentration in lactating cows was not affected (P > 0.05) by experimental diets, but in cows fed with alfalfa silage treated with all varieties of waste dates was shown a higher tendency. Results indicated that using different varieties Brin, Ghybani and Amobahri of waste date in alfalfa silage in level of 6% can improve milk yield and performance of dairy cows.

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