Ruminal, post-ruminal and total tract crud protein disappearance of cottonseed 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, three-step in situ/ in vitro (3-step) and in vitro enzymatic procedures. For the in situ mobile bag technique, four Holstein steers (450±50 kg, body weight) fitted with ruminal fistulae and T-shaped intestinal cannulae were used. Three-step procedure was followed by rumen incubation of samples for 12 h and enzymatic incubation of ruminal undegradable samples. In vitro enzymatic technique was followed by 1 h borate- phosphate buffer incubation, then 4 h in protease solution as ruminal disappearance and enzymatic (pepsin and pancreatin) incubation of ruminal undegradable samples. A significant (P< 0.01) effect was found between the procedures to measure ruminal, post-ruminal and total tract CP disappearance. The protein disappearance of oilseed meals in the rumen and post-rumen determined in vitro enzymatic procedure tended to be higher than 3-step technique. Post-ruminal protein disappearance measured with in vitro procedure was higher (P< 0.01) than in situ mobile bag and 3-step techniques (In vitro= 0.75, In situ mobile bag= 0.74 and 3-step= 0.60; S.E.M= 0.023, respectively). There was a significant (P< 0.01) effect of feeds on ruminal, post-ruminal and total tract CP disappearance. The CSMH had a lower (P< 0.01) ruminal CP disappearance, while the SFM had higher value (0.58 and 0.91, respectively). The CSMH had lower ruminal CP disappearance compared with CSML (0.58 vs. 0.68, respectively). The CSML had a lower (P< 0.01) post-ruminal CP disappearance, while the SBM had higher value (0.59 and 0.81, respectively). In addition, our results indicated that when used to assess post-ruminal disappearance of oilseed meal protein, the 3-step method can underestimate the disappea
