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CAB Reviews

A reviews journal covering agriculture, global health, nutrition, natural resources and veterinary science

CAB Review

Effect of silage characteristics on enteric methane emission from ruminants.

Abstract

This review evaluates the effects of silage characteristics on enteric methane (CH4) emission from ruminants by performing a meta-analysis. A total of 17 studies were selected from the literature, and the relationship between CH4 yield (g/kg dry matter [DM] intake) and silage characteristics was determined using a mixed model univariate regression procedure. For grass silage, organic matter digestibility (%; R2=0.74) and crude protein content (g/kg DM; R2=0.36) were negatively associated, and neutral detergent fibre (NDF) content (g/kg DM; R2=0.44) was positively associated with CH4 yield. This indicates that increased grass silage quality consistently decreases CH4 yield and may be an effective enteric CH4 mitigation strategy. Similarly, optimizing maize silage quality appears to be an effective enteric CH4 mitigation strategy, because NDF content (g/kg DM; R2=0.60) was positively associated with CH4 yield. Upon replacing grass silage with maize silage, dietary starch content (g/kg DM; R2=0.62) and silage replacement level (%; R2=0.33) were negatively associated, and NDF content (g/kg DM; R2=0.34) was positively associated with CH4 yield. These results indicate that replacing grass silage with maize silage consistently decreases CH4 yield and may be an effective enteric CH4 mitigation strategy. In contrast, replacement of alfalfa silage with maize silage was not associated with CH4 yield and does not appear to be an effective strategy to decrease CH4 yield. In conclusion, management practices to improve silage quality are a potent mitigation strategy to reduce enteric CH4 emission per unit of feed fed to ruminants, and implications of silage quality have to be addressed when assessing greenhouse gas emissions in ruminant production.