Abstract: Rumind, p o s t - m k l and total tract cmde protein disappearance of cottomeed meal containing 105 (CSMH) or 65 (CSML) g oil per kg of dry matter (DM), soybean meal (SBM), rapeseed meal (RSM) and sunflower meal (SFM), originating from Iranian plant varieties, were measured using in situ mobile bag, threestep in situlin vitro (?-step) and in vitro enzymatic procedures. For the in situ mobile bag techmque, 4 Holstein steers (450150 kg, body weight) fitted with m i n a l fistulae and T-shaped intestinal cannulae were used. Threestep procedure was followed by m e n incubation of samples for 12 h and enzymatic incubation of m i n a l undegradable samples. In vitro enzymatic technique was followed by 1 h borate- phosphate buffer incubation, then 4 h in protease solution as m i n a l disappearance and enzymatic (pepsin and pancreatin) incubation of ruminal undegradable samples. A significant (p<0.01) effect was found between the procedures to measure minal, post-mind and total tract CP dsappearance. The protein dsappearance of oilseed meals in the m e n and post-men determined in vitro enzymatic procedure tended to be higher than ?-step technique. Postruminal protein disappearance measured with in vitro procedure was higher (p<0.01) than in situ mobile bag and ?-step techmques (In vitro = 0.75, In situ mobile bag = 0.74 and ?-step = 0.60; SEM = 0.023, respectively). There was a significant (p<0.01) effect of feeds onminal, post-minal and total tract CP dsappearance. The CSMH had a lower (p<0.01) m i n a l CP disappearance, while the SFM had higher value (0.58 and 0.91, respectively). The CSMH had lower m i n a l CP dsappearance compared with CSML (0.58 vs. 0.68, respectively). The CSMLhad a lower @<0.01) post-minal CP disappearance, while the SBM had higher value (0.59 and 0.81, respectively). In addtion, our results indcated that when used to assess post-minal disappearance of oilseed meal protein, the ?-step method can underestimate the dsappearance of protein.

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