Effects of dietary and animal factors on methane production in dairy cows offered grass silage-based diets

An analysis of a large dataset, derived from lactating (n = 299) and dry (n = 16) Holstein–Friesian cows offered grass silage-based diets, was undertaken at the Agricultural Research Institute of Northern Ireland. Methane (CH4) produced by cattle was measured in indirect calorimeter chambers. The level of CH4 emission was positively related to live weight, DM intake (DMI), milk yield (MY) and feeding level, respectively (P < 0.001), whereas the latter three variables each had a negative relationship with CH4/DMI or CH4/MY (P < 0.001). The CH4/DMI and CH4/MY ratios increased with increasing dietary silage proportion and concentration of acid and neutral detergent fibre (P < 0.001), but reduced with increasing dietary CP and energy concentration (P < 0.001). The CH4 production can be accurately predicted from DMI or MY together with other animal and dietary variables (R2 up to 0.79). The results suggest that nutritional and management strategies can be used to reduce methane production from dairy cows, for example by increasing productivity or manipulating dietary composition. The reduction in CH4 emission was quantified and discussed in the present paper.