Detalle de: 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 4 ) emissions in the breeding objectives of beef cattle, using the Spanish population of Blonde d′Aquitaine as a case of study. First, CH 4 emissions were included as a cost using a shadow carbon price of 1.22€/ CH 4 kg (0.044€/ CO 2 kg) (carbon tax scenario). In the other scenario, a CH 4 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 4 was calculated under all scenarios using a bioeconomic model that translated the production system into a mathematical function. Then, CH 4 emissions were included with proper relative weight in the selection index under each scenario. The economic value of CH 4 production from cows was −0.54€/year and −0.16€/year in a carbon tax and in a CH 4 quota scenario, respectively. Economic values for CH 4 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 4 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 4 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 4 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.