Prediction of nylon bag degradation characteristics of grass samples with the gas production technique

Samples were taken from grass (Lolium perenne) fertilised with different N-levels, varying from 150 to 450 kg N ha−1 per year and harvested from late spring to late summer. Degradation characteristics and kinetics were determined both in situ, using the nylon bag technique and in vitro, using the gas production technique. With both techniques, the rate of degradation of the high fertilised grass was higher than of the low fertilised grass. Also, with both techniques, the rate of degradation of grass cut in late summer was higher than that of grass cut in late spring or early summer. The degradation rate (kd) of organic matter and of the NDF fraction, measured with the nylon bag technique, could be estimated (R2=0·87-0·89) from gas production parameters. Also the amount of fermentable organic matter (FOM) could be estimated accurately (R2=0·93-0·96) from gas production parameters. It is concluded that the gas production technique and the used curve fit model offers a cheap, fast and accurate alternative for estimating feeding values of grass with the nylon bag technique.