Northern Australian tropical pastures transition through dry periods of low rainfall and limited nutritional value which presents challenges in terms of animal productivity and lifecycle methane emissions.This study was conducted to utilize in vitro gas production to assess the methane contribution from tropical forages differing in harvest date and N content.The Ankom Gas Production system was used to measure differences in total gas production (TGP) between Barley Mitchell (Astrebla pectinata) pasture collected in wet (March/May) and dry season (Aug/Nov) northern Australia.Analysis of variance showed an effect of harvest date on in vitro organic matter digestibility (IVOMD, P<0.001), and total volatile fatty acids (VFAs, P<0.05).Total gas production per g digestible organic matter (DOM) was not affected by date of harvest but methane production per 1 g DOM was greater (P<0.01) in March.