Diet has a direct effect on CH4 emissions from enteric fermentation and an indirect effect on CH4 emissions during storage, by affecting manure composition (Hindrichsen et al., 2005).
Decreased digestibility of dietary nutrients is expected to increase organic matter concentration in manure, which may increase manure CH4 emission. The effect of diets on denitrification and N2O emission is related to the animal protein balance. An excess dietary protein will increase N excreted in manure and N2O emission following land application. A reduction in manure N concentration will also reduce manure N2O emissions (Misselbrook et al., 1998). Inclusion of some natural compounds (such as tannins from pasture legumes, e.g. from birdsfoot trefoil) in the diet can increase the proportion of N excreted as organic N by faeces and reduce the excretion of urea-N in urine, thereby reducing the potential for NH3 and N2O emissions (Misselbrook et al., 2005). However, such dietary changes may also affect the animal protein supply.
Source: AnimalChange (project supported by the EU-FP7)
DELIVERABLE 6.2. Deliverable title: Report on the extent to which manure management might help decrease GHG gas from animal agriculture.