Plant-based methane inhibitors for cows in mountain grassland regions: land requirements to realize effects

Summary in the original language of the document

Mitigating methane emissions from enteric fermentation is a challenge also for grass-based cattle production systems in mountain regions. Since increasing concentrate amounts or using synthetic inhibitors is often no option for various reasons, plant-based feed additives are often mentioned as a chance. We systematically reviewed existing literature including herbs or oil-plants, which grow in European climats. Inclusion condition was the presence of at least three independent in vivo studies for the specific plant. We assessed the average size of effects. Furthermore, we calculated for the example of Switzerland, how much arable land for plantation would be required to archieve the dosages used in the published experiments for the whole Swiss cattle population. For all canditate herbs, the effect was lower than 10% reduction of CH4 per unit of intake. Average effects of higher than 10% were only reached with plant oils (rapeseed, sunflower and linseed) and grape marc. For all interventions fulfilling the minimal number of experiments, land-requirements to archieve the dosages for the total Swiss cattle population reached from 70 to 130% of Swiss agricultural area. The only exemption was Origanum vulgare, which would require only 11% of Swiss arable land, however with an average published CH4 mitigation effect of approximately 3,5%. In conclusion, to date there are only few plants applications suitable for European mountain regions, which are proven in vivo with at least three experiments, an more of them shows a reasonable relation between effrt and impact. There is not enough literature for a generalisable assessment of the effects of herbs with mitigation potential if they are included in multispecies pasture swards.