The use of a syringe (manual method) to measure gas production is time consuming and inaccurate. In addition the time taken prevents frequent measurements and therefore does not allow gas production kinetics to be fully described. According to Boyle's Law, gas volume corrected for temperature, is directly related to pressure. A simple, semi-automatic system recording of gas pressure and equations to estimate volume, was therefore developed.
Data for this work came from a study which compared rumen liquor and faeces as sources of inoculum using the method of Theodorou et al. (1994). Six substrates (wheat straw, hay, soyabean meal, wheat starch, maize starch, and potato residue) were utilized. Gas pressure readings (observations = 1187) were measured using a hand-held pressure transducer with an LED readout. Interfaced to a computer using a Mini-Pod 300 (AD converter). MS-Visual Basic (Microsoft) was used to convert the mini-pod readings and automatically enter them into an Excel spreadsheet. Gas volume was measured using a syringe to remove the gas produced until the readout indicated zero.