Rumen Fermentation Kinetics of Grass Measured in Sacco and with the Gas Production Technique

17-35 ABSTRACT Rumen fermentation kinetics of grass and silage, differing in age and yield (1500 -7900 kg DM ha), were studied in sacco and in vitro, using the gas production test and the Tilley and Terry technique. An increasing yield increased the content of NDF and lignin in grass and decreased protein content, in vitro degradability measured by the Tilley and Terry method, and rate of fermentation measured with the gas production technique and the nylon bag method. The same ranking in fermentation characteristics was observed using the gas production test, the nylon bag method and the Tilley and Terry method. The gas production test proved an accurate, reliable and cheap alternative for the in sacco technique to determine differences in fermentation characteristics between different grass and silage samples in the rumen.