A COLLABORATIVE STUDY OF IN-SITU FORAGE PROTEIN-DEGRADATION

An in situ procedure was used in four collaborative trials to evaluate the variation in estimates of ruminal escape protein among eight labo ratories. A standard smooth bromegrass hay was established and evaluat ed in all four trials, and Trials 3 and 4 also included the standard h ay material that was retained on a 75-mu m sieve. Polyester bags (10 c m x 20 cm) containing 5 g of sample were soaked in water (39 degrees C ) for 20 min and incubated ruminally for 16 h in a bag made of mesh ma terial. Bag rinsing after in situ incubation consisted of a primary ph ase in which the mesh bags containing sample bags were washed with wat er (39 degrees C) in 19-L white plastic buckets. Repeated cycles of fi lling, agitating, and dumping were performed until the rinse water was clear. Secondary rinsing was performed on individual bags by rinsing the exterior with water (39 degrees C) followed by rinsing through the unsealed opening the interior residue to the bottom of the bag for 1 min (Trials 1 and 2). Secondary rinsing for Trials 3 and 4 was the sam e as for Trial I, but with only enough water (39 degrees C) and time t o rinse the residue to the bag bottom. Mean estimates of escape protei n (EP/CP) were: Trial 1, 27.4 +/- 3.08; Trial 2, 30.8 +/- 3.21; Trial 3, 31.1 +/- 3.04 (non-sieved); and Trial 4, 27.7 +/- 3.06 (non-sieved) . Reasonable control of error was accomplished by technician training, including the use of a videotape to clarify the procedure. The videot ape emphasized the techniques required through the rinsing phase to co ntrol error. No difference was observed in escape protein estimates be tween sieved or non-sieved material (P > .2). Development and use of a standard in situ rinsing procedure is recommended to minimize variati on among laboratories.