Ruminant efficiency

Methane (CH₄) is produced as a side-effect of the high bacterial activity in the rumen and released into the ambient air during rumination. Methane is 25 times more potent than carbon dioxide (CO₂) in terms of climate effect, however much more short-lived (CO₂ remains in the atmosphere for 800-1000 years, CH₄ less than 13 years). Recently, the contribution of agriculture was 41% of anthropogenic CH₄ emissions¹, with a large share due to enteric fermentation². CH₄ should therefore be considered as the most dominant climate gas within agriculture. Feeding strategies geared towards this currently focus on efficiency per unit of food produced.

The comparison of climate gas emissions and their effect on each other is made using the conversion unit "CO_² equivalent". On a global average, the production of one litre of milk releases methane in the order of about 2.4 kg CO_² equivalent. The wide range between 1.1 kg in countries with highly specialised dairy husbandry and 7.5 kg in regions of extensive husbandry under adverse conditions results from the interaction of breeding, husbandry and feeding in view of local resource availability. The use of mixed rations has been shown to reduce methane emissions compared to pure extensive grazing.³

Research on feed-related reduction of CH₄ from enteric fermentation has increased exponentially over the last two decades, with various strategies being investigated: Intensification of production, feed optimisation (including processing of concentrates and fats, targeted supplementation of functional nutrients, and forage production and pasture management), rumen manipulation via feed additives (botanicals and others). For extensive production systems without feed supplementation, there are currently few options to reduce CH₄ emissions.⁴