In situ degradable parameters and m i n a l and post m i n a l dsappearances of Dry Matter (DM) and Cmde Protein (CP) of a variety of Iranianrapeseed meal (SLM sp.) were determined. Then, 14 early lactating Holstein cows for 8 weeks were fed diets containing 10.95% Soybean Meal (SBM) or 10.85% Rapeseed Meal (RSM) in a completely randomized design with repeat measurement analysis. Dry matter intake and milk yield were measured daily and milk composition were measured weekly. Bloodmetabolites includng glucose and non amino-N were measured in weeks 1, 4, 6 and 8. Feces pH was monitored at weeks 4 and 8. Degradable coefficients of RSM includq rapidly, slowly andFractiona1 degradation rate, were 0.32, 0.49 and 0.092 for DM and 0.33, 0.58 and 0.1 2 for CP, respectively. Ruminal and post m i n a l dsappearance of DM and CP were 0.68, 0.52 and 0.71 and 0.66, respectively. Dry matter intake (kglcowlday) was significantly (p<0.05) influenced by the dets (RSM= 19.9, SBM= 20.5, SEM = 0.21). Mdkproteinandmilk solidnon-fat of cows fedRSM(28.88 and 86.03, respectively) were significantly higher (p<0.05) compared with animals fed SBM (27.63 and 81.8, respectively). Milk fat lactose and urea nitrogen, fecal pH and BCS were all similar between dets (p>0.05). Data of the present experiment indicated that the Iranian variety of RSM might be used in hgh producing lactating Holstein cows without any adverse effect.

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