Methane emissions are lower from reindeer fed lichens compared to a concentrate feed

Abstract

Methane emissions from reindeer (Rangifer tarandus tarandus) fed lichens (mainly Cladonia stellaris) and a concentrate feed were determined using open-circuit respirometry. The lichen diet was low in crude protein (< 2.6% of dry matter [DM]), starch (6.0% DM) and acid detergent lignin (2.0% DM) compared to the concentrate feed (12.7, 22.5 and 7.2% DM, respectively), and high in neutral detergent fibre (82.2% DM versus 34.8% DM in concentrate feed). The feeds were offered in equal amounts (ca. 0.440 kg DM) 2 h after initiating methane recordings in the respiration chamber. The reindeer were adapted to these diets for > 4 weeks prior to experiments and methane emissions recorded for two separate 23 h periods for each diet. Methane emissions increased on average by 0.93 g/h (or by 5.8 times) in the first hour after feeding the concentrate feed, while emissions remained unchanged after the intake of lichens. Mean methane emissions from reindeer (n = 5) were 7.5 ± 0.54 (SE) g CH4 day−1 when fed lichens, compared to a higher emission (p = 0.001) of 11.2 ± 0.54 g CH4 day−1 on the concentrate diet. The mean proportion of gross energy intake lost as methane was 5.2 ± 0.37% on the lichens and 7.6 ± 0.37%, or some 50% higher, on the concentrate feed. This difference was significant (p < 0.001). Our results suggest that it is of environmental importance to preserve the lichens on the tundra and minimize supplementary feeding with concentrate diets, in order to reduce methane emission.