Utility of an in vitro test with rumen fluid from slaughtered cattle for capturing variation in methane emission potential between cattle types and with age

Differences in methane emission between cattle types and 273-4903-d-old cattle were evaluated. Rumen content from 59 beef and 32 dairy cattle, collected at an abattoir, was used for in vitro incubation with a forage-based diet alone or supplemented with extruded linseed. Incubating rumen fluid from dairy cows yielded lower methane per gram of diet dry matter (DM) incubated (-5.5%), methane/total gas ratios (-8.5%), and ammonia concentrations (-38%) than that from beef cattle. Linseed decreased methane yield (-6.5%), total gas production (-3.6%), and methane/total gas ratio (-2.7%). High emitters responded slightly more to linseed than low emitters. Lower methane yield (-15%), total gas (-11%), and ammonia concentrations (-20%), and a trend for lower methane/total gas ratios (-5.2%) were found in Limousin x Brown Swiss than in Limousin x Holstein. In beef cattle, methane yield increased (up to 40 mL g(-1) DM) with age in a linear manner, whereas in overall dairy and beef animals the relationship was curvilinear (high in young and old animals) concerning methane/total gas ratio and ammonia concentration (trend in beef). In conclusion, rumen fluid from slaughtered animals may be useful to study variations in methane emission from different cattle types.