As a consequence, higher daily CH4 emission would be expected; however, the high NDF digestibility of soybean hulls could improve animal performance and lower CH4 yield (g/kg of DMI) or intensity (g/kg of milk). To the best of our knowledge, no in vivo studies have been conducted to evaluate the effect on rumen methanogenesis of partial replacement of corn meal by soybean hulls. Furthermore, as reported by Martin et al. (2010), only a few studies have been conducted to evaluate the effects of the nature of concentrate on methanogenesis.