Methane emissions intensity in grazing dairy cows fed graded levels of concentrate pellets

The current New Zealand greenhouse gas inventory predictions assume that dairy cows consume pasture only, but the use of supplemental feeds, including concentrates, on New Zealand dairy farms has increased greatly in recent decades. The objective of this study was to evaluate the effect of feeding graded levels of concentrates on methane (CH4) emissions in lactating dairy cows within a pastoral system. Early lactation dairy cows (n = 72) were allocated (n = 18 per treatment) to receive 0, 2, 4 and 6 kg dry matter (DM) of treatment concentrates per day during milking. The cows grazed pasture ad libitum and CH4 emissions were measured in the paddocks using automated emissions monitoring systems called 'GreenFeed'. Gross CH4 emissions (g/d) were similar for cows across the four dietary treatments, while CH4 emissions intensity (g/kg fat and protein corrected milk production (FPCM) and milk solids production) linearly decreased with increasing concentrate inclusion in the diet (P < 0.02). The CH4 intensity decreased linearly (r(2) = 0.42) and quadratically (r(2) = 0.53) with increasing FPCM production.