Selection indices offer potential for New Zealand sheep farmers to reduce greenhouse gas emissions per unit of product

The New Zealand Government is a signatory of the Kyoto Protocol which provides incentive for it to reduce its total greenhouse gas emissions (GHG). The sheep industry is a significant contributor to the total GHG in New Zealand. It also has widespread use of selection index technology which could be a potential GHG mitigation tool. This paper provides an assessment of the potential for New Zealand sheep farmers to reduce GHG using selection indices. Trait weightings were altered in novel indices to facilitate greater reductions in GHG. These were compared to a conventional farm profit maximising index. Selection of sheep using the farm profit maximising index reduced GHG output in kilograms of carbon dioxide equivalent units (kg CO2e) per kilogram of lamb carcase weight (kg cwt) by 0.59% of total methane and nitrous oxide emissions per annum (pa). Novel ‘Dual Purpose Environment’ indices (DPE) were developed to provide greater GHG reductions in kg CO2e/kg cwt. A range of carbon prices were incorporated into the DPE. The study showed 96.6% of the potential farm profit (excluding emissions costs) and 69.8% of potential kg CO2e/kg cwt improvements could be obtained using a carbon price of NZ$100/tonne CO2e in the DPE. The corresponding figures for NZ$25/t CO2e were 99.8% and 56%. The carbon price used in the DPE therefore influenced the trade-off between progress in traits which reduce GHG in kg CO2e/kg cwt and those that improve farm profitability. Selection indices are an option for farmers to reduce GHG in kg CO2e/kg cwt in New Zealand sheep. However, farmers will need to consider the trade-off between improving traits which contribute to farm profit and those that reduce GHG.