Expected consequences of including methane footprint into the breeding goals in beef cattle. A Spanish Blonde d'Aquitaine population as a case of study.

This study evaluates two potential scenarios for including methane (CH ) emissions in the breeding objectives of beef cattle, using the Spanish population of Blonde d'Aquitaine as a case of study. First, CH emissions were included as a cost using a shadow carbon price of 1.22€/CH kg (0.044€/CO kg) (carbon tax scenario). In the other scenario, a CH quota was applied, optimizing emissions per unit of product. The current production system was used as benchmark scenario (Scenario 1). The economic value of CH was calculated under all scenarios using a bioeconomic model that translated the production system into a mathematical function. Then, CH emissions were included with proper relative weight in the selection index under each scenario. The economic value of CH production from cows was -0.54€/year and -0.16€/year in a carbon tax and in a CH quota scenario, respectively. Economic values for CH production from fattening calves were -1.22€/year and -0.34€/year in a carbon tax and a quota scenario, respectively. The relative weights of total CH traits in the indices were 4.9% and 1.8% in a carbon tax and quota scenario. The carbon tax scenario led to smaller cows (-7.59 kg of mature weight) and a decrease in carcass weight gain of calves (-4.78 g/day) involving a reduction in emissions in comparison with Scenario 1 (-0.76 CH kg/slaughtered calf/year). However, it also led to a lower expected gain in profit per unit of product (-7.86 €/slaughtered calf/year). A carbon quota scenario would select slightly smaller cows (-0.48 kg) with similar responses in maternal abilities (age at first calving, calving interval, maternal weaning weight, and calving ease) and growth, and lower emissions (-0.22 CH kg/slaughtered calf/year) regarding the benchmark scenario. Profit per cow would increase by +1.52€/slaughtered calf/year although this scenario implies a reduction in the number of cows per herd. In a carbon tax scenario, higher reduction in emissions implied a reduction of profitability per animal.