Can GreenFeed automated emissions monitoring systems measure methane output from young red deer grazing pasture?

There are limited data on the methane output of pasture-grazed farmed red deer (Cervus elaphus) in New Zealand. Identification and validation of methane-mitigation strategies for farmed deer requires a technology that can be deployed under grazing conditions. The GreenFeed automated emissions monitoring system (GAEM) integrated with an automated concentrate feeder has been successfully used to determine methane output from cattle but has not been tested with deer. The objective of this study was to evaluate large and small ruminant GAEM units with rising-yearling red deer, to determine if they would access the feed lure, and remain for sufficient duration in the hood of the unit to collect representative measurements of methane outputs. Groups of 14 mixed-sex red deer were used in three trials during spring of 2020. In each trial, approximately a third of individuals accessed the GAEM units after being habituated to the lucerne pellet lure, more than 85% of visits were < 2 min. With further refinement of deer-training protocols and configuration of the GAEM, pasture-based methane outputs should be able to be measured for a proportion of any mob with access to the unit.