Effects of different barley and oat varieties on methane production, digestibility, and fermentation pattern in vitro

摘要

The objective of this in vitro study was to determinethe effects of different barley and oat varieties on CH_4production, digestibility, and rumen fermentation patternsin dairy cows. Our hypothesis was that oat-baseddiets would decrease CH_4 production compared withbarley-based diets, and that CH_4 production would differbetween varieties within grain species. To evaluatethis hypothesis, we conducted an in vitro experimentusing a fully automated gas production technique, inwhich the total gas volume was automatically recordedby the system. The experiment consisted of triplicate48-h incubations with 16 treatments, including 8 differentvarieties of each grain. The grain varieties wereinvestigated as a mix with an early-cut grass silage(1:1 ratio of grain to silage on a dry matter basis) andmixed with buffered rumen fluid. We estimated predictedin vivo total gas production and CH_4 productionby applying a set of models to the gas production dataobtained by the in vitro system. We also evaluated invitro digestibility and fermentation characteristics. Thevariety of grain species did not affect total gas production,CH_4 production, or fermentation patterns in vitro.However, in vitro-determined digestibility and pH wereaffected by variety of grain species. Grain species affectedtotal gas and CH_4 production: compared withbarley-based diets, oat-based diets decreased total gasproduction and CH_4 production by 8.2 and 8.9%, respectively,relative to dry matter intake. Grain speciesdid not affect CH_4 production relative to in vitro truedry matter digestibility. Oat-based diets decreased digestibilityand total volatile fatty acid production, andmaintained a higher pH at 48 h of incubation comparedwith barley-based diets. Grain species did not affectfermentation patterns, except for decreased molar proportionsof valerate with oat-based diets. These resultssuggest that replacing barley with oats in dairy cowdiets could decrease enteric CH_4 production.