摘要 : The objective of the present study was to estimate methane production using the kinetic parameters from an automated <i>in vitro</i> gas production (GP) system in a mechanistic, dynamic rumen model. Four sample sizes [300 mg (5 g/... 展开 The objective of the present study was to estimate methane production using the kinetic parameters from an automated <i>in vitro</i> gas production (GP) system in a mechanistic, dynamic rumen model. Four sample sizes [300 mg (5 g/l), 600 mg (10 g/l), 900 mg (15 g/l) and 1200 mg (20 g/l)] of timothy hay were incubated in 60 ml buffered rumen fluid in an automated <i>in vitro</i> system to determine methane and total gas production. A logarithmic model (<i>R</i>²>0.99) was fitted to methane data to estimate methane concentrations at time intervals of 0.2 h. The first-order gas production rates were not different (P=0.18) with values of 0.072, 0.061, 0.061 and 0.059/h for the sample size of 300, 600, 900 and 1200 mg, respectively. The methane production rates were 0.052, 0.046, 0.046 and 0.045/h, respectively. Predicted methane production decreased linearly (PLIN<0.01) as the sample size increased from 300 (36.9 ml/g dry matter, DM) to 1200 mg (28.2 ml/g DM). After 48 h of incubation total volatile fatty acids (VFA) production decreased (PLIN<0.01) as the sample size increased from 300 to 1200 mg (4.41 mmol/g DM and 3.82 mmol/g DM, respectively). Neutral detergent fibre digestibility (aNDFomD), apparent organic matter digestibility (AOMD) and true organic matter digestibility (TOMD) decreased (PLIN=0.01) as the sample size increased (0.479, 0.433 and 0.681 for 300 mg, and 0.369, 0.379 and 0.614 for 1200 mg of sample size, respectively). Actual methane production (24 and 48 h of incubation) was strongly correlated (<i>R</i>²=0.97) with the methane production predicted from VFA stoichiometry (VFA measured at 24 and 48 h of incubation). It is concluded that <i>in vitro</i> GP measurements can be successfully used to estimate kinetic parameters of methane production and consequently to predict methane production. It seems that sample size did not affect the first-order production rate of methane and therefore, it is possible to use greater amounts of substrate in the <i>in vitro</i> GP system up to 1000 mg (16.6 g/l). 收起