Fat and methane

Methane is produced in the rumen as a result of fermentation of feed. Adding fats to diets can lower methane emissions and hence reduce agriculture’s contribution of this greenhouse gas. Fats can either act as ‘sinks’ to mop up the hydrogen atoms produced during fermentation which would otherwise be released as methane gas (rumen-active fats), or reduce the raw materials for methane production by replacing fermentable feed in the rumen. Methane also represents a significant loss of feed energy from the animal - up to 12 % of feed energy intake (gross energy) can be lost as methane from ruminants.

Research work has demonstrated the effect of increasing fat concentration of dairy diets on methane production. Using calorimetric chambers, Andrew et al. (1991) determined methane production of dairy cows following substitution of maize grain with Megalac rumen-protected fat (2.95% of dry matter) and reported a 13.7% reduction in methane output per unit of milk production (Table 1).

Table 1      Effect of adding Megalac to a diet on methane production


Control (no fat supplement) Control + Megalac Sig.
Milk yield (kg/d) 32.0 34.3 P<0.01
Methane (litre/d) 539 498 P<0.05
Litres methane / kg milk 16.8 14.5 13.7% reduction