The effect of age on methane emissions from young, weaned red deer ( Cervus elaphus ) stags grazing perennial‐ryegrass ( Lolium perenne)‐based pasture

Sheep less than 1 year of age consistently yield approximately 20% less methane than older adult sheep. This has implications for New Zealand's National Inventory of Greenhouse Gas Emissions. The aim of this study was to determine if emissions from young farmed deer also increase with age. Methane emissions of 20 red deer stags grazing permanent perennial ryegrass‐based pasture were measured four times post‐weaning, at 4.5, 6.5, 9 and 11.5 months of age, using the sulphur hexafluoride technique. Methane production and methane yield increased with age ( P < 0.05) and appeared lower (26%) than previous measurements from adult deer on similar pasture. The results from this study imply that total methane emissions from young deer recorded in the New Zealand greenhouse gas inventory are likely to be overestimated if values used for the inventory are based on adult methane emissions.