Dose-response and inclusion effects of pure natural extracts and synthetic compounds on in vitro methane production

Comparison of five methods for the estimation of methane production from vented in vitro systems

“…Mean differences between estimated methane production for each incubation by methods B, C, D and E and actual methane production, measured by method A, with 95% confidence intervals.…”

“…Methods D and E allowed for the calculation of MP from vented systems without the collection of the vented gas and without counting the number of ventings, ultimately reducing costs and labour. Method D had been validated in a previous study; however, the development of the equation was never described and the authors provided only a very limited description of a validation study involving just three concentrates and four forages in 42 bottles . Method E is based on the assumption that the VCH 4 /HSCH 4 is approximately equal to 0.5.…”

“…Method D was an empirical method developed using the Ankom GP system . It also used GP and HSCH 4 to estimate MP: …”

“…The gold‐standard method for estimating MP involves measurement of total GP collection of all the vented gas in a gas‐tight collection bag and measurement of HSCH 4 and VCH 4 . Four methods that use a single gas sample taken from the headspace at the end of the incubation have been proposed . One of these methods involves estimating MP as the sum of the headspace gas volume in the incubation vessel, plus the volume of gas produced, multiplied by the proportion of methane in the headspace at the termination of the incubation .…”

“…Two of these methods are calculated through algorithms and rely on the assumption of a constant methane to carbon dioxide ratio . A fourth method involves an empirical equation for predicting MP . To our knowledge, there are no studies that have compared these different methods and tested or ranked their agreement against the gold‐standard method under a wide range of incubation scenarios.…”