372 Effect of rumen fluid collection methodology on extent and variance of in vitro dry matter disappearance and interaction with substrate and incubation time

Abstract

Abstract The objective was to evaluate the interaction of rumen fluid collection methodology, substrate, and incubation time on the extent and variance of in vitro dry matter disappearance (IVDMD). A 4×2×2 factorial design was used to test the interaction between rumen fluid collection methodology, substrates (hay and silage), and incubation time-points (24 and 48 h). Four methods of rumen fluid collection were evaluated: stomach tube (TUBE), suction strainer through rumen cannula (STRN), ruminal contents collected through cannula and squeezed through cheesecloth (SQZ), and ruminal contents blended for 1 minute and squeezed through cheesecloth (BSQZ). Four replications of each treatment were used and repeated in three periods. A methodology by substrate interaction (P < 0.01) was observed for pH; hay had a greater pH than silage and the magnitude of this difference was greatest for STRN. A tendency for a methodology by substrate interaction (P = 0.06) was observed for ammonia. For TUBE ammonia was greater (P < 0.01) with hay while substrate did not affect ammonia for BSQZ, SQZ and STRN. A methodology by time interaction was observed (P < 0.01) for ammonia; TUBE was least at 24 h, but TUBE and BSQZ were lesser (P ≤ 0.01) than STRN and SQZ at 48 h. A tendency for a methodology by substrate interaction (P = 0.08) was observed in IVDMD; silage had greater IVDMD than hay and the magnitude of this difference was greatest for TUBE. Collection methodology affected (P < 0.01) IVDMD. The greatest IVDMD was observed for STRN (64.7%), with BSQZ (59.1%) and SQZ (57.7%) being intermediate and TUBE (54.3%) being the least. A tendency for a methodology by substrate interaction (P = 0.11) was observed for variation in IVDMD; silage had greater variation than hay for TUBE. Rumen fluid collection methodology affects IVDMD and may depend on substrate.