Comparison of dry matter and neutral detergent fibre degradation of fibrous feedstuffs as determined with in situ and in vitro gravimetric procedures

Our goal was to compare two technical approaches (the in situ nylon bag technique, IS, and an in vitro gravimetric procedure using DaisyII, IV DaisyII) to estimate DM and NDF degradation kinetics of fibrous feedstuffs. Evaluated feedstuffs were four fresh pastures, two high dry matter forages, and two agro-industrial by-products. In the IS, two 2 bags (polyfilament, 5 cm × 9 cm, pore size 50 ± 15 μm, ANKOM 1020) of each feedstuff were incubated (2, 4, 8, 12, 24, 48, 72 and 96 h, 2 consecutive periods) in the rumen of three wethers. In the IV DaisyII, six bags (5 cm × 3 cm, mean pore size 45 μm) of each feedstuff were incubated (same schedule as IS) in digestion jars with a buffer/fluid ruminal solution (80:20). Compared with IS, IV DaisyII underestimated DM and NDF disappearance, and the largest differences between procedures were observed at early incubations times. Both procedures ranked feedstuffs similarly for their DM effective degradability suggesting the IV DaisyII procedure may be a useful tool to compare degradation potential of feedstuffs. Further investigations are needed to study the variations observed in the early incubations times between the two procedures.