An investigation of methane emissions from beef cattle grazing contrasting upland and lowland vegetation types

The principle aim of the studies reported within this thesis was to quantify and compare methane emissions from beef cattle consuming upland vegetation and lowland vegetation. Within this remit, methods to estimate intake and methane emissions were evaluated and the data acquired through these methods were used to contextualise the estimated methane emissions against levels of intake and animal performance. Cattle grazing upland vegetation were found to produce greater absolute amounts of methane (g/d) than those consuming lowland vegetation, but cattle consuming lowland vegetation had greater DM intakes and body-weight gains. There was no significant difference in methane g/kg DMI between cattle grazing upland and lowland vegetation. The studies indicated that DM intake is a significant driver of methane production by beef cattle. There were significant differences in methane emissions (when expressed as g/kg DMI) between housed cattle offered upland and lowland vegetation but any difference between vegetation types ceased to be significant when methane was expressed as g/kg digestible DMI. However, cattle consuming upland vegetation had significantly greater methane emissions per unit of BWG (kg/d) than cattle consuming lowland pasture. This study has shown that a modified l1-alkane protocol (incorporating once-daily alkane dosing and once-daily faecal sampling) can be used to reliably estimate DM intake by grazing beef cattle. Across all of the studies conducted, there were no breed (suckler vs dairy origin) differences between cattle for DM intake, absolute methane emissions, bodyweight- gains or methane emissions expressed as % of gross energy intake. The study reinforced the usefulness of GPS collars when used in conjunction with vegetation measurements, maps, and visual observations to monitor animal distribution, grazing behaviour and identify the diet selection by cattle grazing on heterogeneous upland pastures. Strategies to mitigate methane emissions from grazing cattle on the upland are currently limited and require further investigation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo