Effects of grain-based concentrate feeding and rumination frequency on the milk production, methane and carbon dioxide fluxes, and activity of dairy cows in a pasture-based automatic milking system

Abstract The warming effect of ruminant greenhouse gases is an issue of increasing global concern. In this experiment the abatement of ruminant gases by offering three levels of grain-based concentrate (GBC) to dairy cows of high and low rumination frequency was tested in a pasture-based, automatic milking system. Two groups of 30 cows (milk yield = 35 ± 2 kg/d), with consistently high (HR; 619.9 ± 8.9 min/d) or low (LR; 472.5 ± 10.2 min/d) rumination frequency were selected and assigned to either a low (LGBC), medium (MGBC) or high (HGBC) grain-based concentrate feeding treatment (n = 10 cows/treatment) that included a standard grain-based pellet ration of 7 kg DM/cow/d plus 0, 1.5 or 3 kg DM/cow/d of shelled corn, respectively. Cows on all treatments were also offered the same temperate pasture at 30 kg DM/cow/d that was split evenly between two fresh pasture breaks. Milk production, rumination frequency, activity, mass flux of enteric methane (QCH4) and expired carbon dioxide (QCO2), and dry matter intake (DMI), determined empirically by use of QCO2 as a biomarker, were recorded for 12 d and analysed with mixed models for a completely randomised design. No effect of rumination on QCH4 or QCO2 was detected. Offering HGBC decreased (P = 0.02) DMI and QCO2. Offering HGBC also reduced (P