Twenty-four lactating Holstein dairy cows were used in a completely randomized design to investigate the effect of soybean meal (SM) and xylose protected soybean meal (XSM) in combination with ground (GB) or steam flaked (FB) barley on dry matter intake, milk production, rumen fermentation and blood responses. The experimental period lasted for 30 days. The diets consisted of the provision of 19.85% corn silage, 12.02% alfalfa hay, 0.72% wheat straw and 67.41% concentrate that averaged 17% crude proteins (DM basis) were offered two times daily. Dry matter intake (DMI) (P=0.051) and milk yield (P<0.0001) decreased by XSM in diets with GB or FB (P<0.05). The animals fed diets containing XSM had lower fat corrected milk (FCM 3.5%) and energy corrected milk (ECM) than diets containing SM (P<0.05). The milk fat and solids not fat percentage in XSM were significantly higher than SM (P<0.05) but milk protein percentage was lower (P<0.05). A comparison of GB versus FB and SM versus XSM diets indicated that the milk protein yield was higher for diets containing FB (P<0.05) and containing SM (P<0.001). Blood metabolites were significantly different between treatments (P<0.05). The diets containing XSM had lower levels of non-esterified fatty acids and higher levels blood urine nitrogen than those containing SM (P<0.05). The Acetate, propionate, valerate and butyrate concentrations differed significantly between the diets (P<0.05). In according to the results of our experiment, soybean meal in combination with ground barely may alter the performance of Holstein dairy cows.

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