1Ph.D. Student in Ruminant Nutrition, Department of Animal Sciences (Excellence Center for Animal
Sciences), College of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
2Department of Animal
Sciences (Excellence Center for Animal Sciences), College of Agriculture, Ferdowsi University of Mashhad,
Ruminal, post-ruminal and total tract crude protein disappearance of alfalfa hay and barley grain were measured using in vivo, in situ mobile bag and three-step in situ/in vitro enzyme procedures (3-step). For in vivo, four Baluchi lambs (49.4 ± 3.5 kg, body weight) were used in a 2 × 2 Latin square design within 2 periods (24 days of each period). Experimental diets were made of two alfalfa hay: barley grain ratios (DM basis) as 1.0:0.0 and 0.5:0.5. Diets were fed to animals for 24 days, with 7 days of feces collection. In situ mobile bag technique was followed by 12 h rumen incubation and then intestinal movement of the bags in rumen and post-rumen cannulated Holstein steers. The three-step procedure was followed by rumen incubation of samples for 12 h (using polyester bags) and enzymatic incubation of ruminal undegradable samples. In vivo total tract crude protein disappearance of alfalfa hay and barley grain (0.74 and 0.69, respectively) was significantly (P<0.01) lower than in situ mobile nylon bag (0.89 and 0.96, respectively) and the 3-step procedure (0.81 and 0.89, respectively). Total tract crude protein disappearance from in situ mobile bag was significantly (P<0.01) higher than the 3-step technique. Post-ruminal disappearance of ruminal undegradable crude protein from alfalfa hay and barley grain using in situ mobile bag method (0.69 and 0.86, respectively) was significantly (P<0.01) higher than the 3-step enzymatic method (0.49 and 0.56, respectively). Results of the present study showed that there was a significant difference between in vivo, in situ mobile bag and 3-step methods when total tract crude protein disappearance of barley grain and alfalfa hay was evaluated.