Methane and carbon emissions from conventional pasture and
grain-based total mixed rations for dairying
L.S. VAN DER NAGEL, G.C. WAGHORN AND V.E. FORGIE
Department of Resource and Environmental Planning, Massey
University, Private Bag 11222, Palmerston North, New Zealand
E-Mail:
NZSAP 2003 Abstract No. 31
Proceedings of the New Zealand Society of Animal Production
63: 128-132
Comparisons between cows grazing pasture or fed total mixed
rations (TMR) show on average less milk production from pasture but a
higher methane yield per milk or milksolids production from the pasture
diet. The implication that TMR are associated with relatively lower
greenhouse gas (GHG) emissions than pasture required an assessment of
all production costs associated with both systems because TMR requires
extensive cultivation and processing of grains and silages which form
the bulk of the diet. A partial life cycle analysis of GHG (excluding
nitrous oxides) was carried out for separate 250 cow herds located in
Waikato (pastoral grazing) and Canterbury (cropping land for the TMR).
This demonstrated much higher methane and carbon dioxide emissions, (kg
CO2 equivalents/kg milk) from cows fed TMR (1.53) relative to
pasture (0.84). The principal cause of the high value for TMR were
carbon losses from soil cultivation which accounted for 64% of
emissions, expressed as CO2 equivalents compared to 24% from
pasture. Enteric methane accounted for 28% of GHG from TMR and 64% from
pastoral systems. The remaining 8% and 12% from TMR and pastoral grazing
respectively, were attributed to fertilisers, cultivation and
processing.
Keywords: NZSAPAB;
Dairy production; greenhouse gases; methane; carbon dioxide;
total mixed rations; pasture
Last Updated 8/07/2004
