Efficient pigs do not always have less environmental impacts: insights from an individual-based model to assess...

Pig production is facing economic and environmental challenges. In previous studies, the environmental impacts of pig farming have mainly been assessed with group-feeding strategies. A feeding strategy applied to a group of pigs results in unequal animal responses and environmental impacts due to inter-individual variability in lean growth potential and nutritional requirements. The present work aimed at fairly evaluating pigs' responses in a given production system. We designed a methodological approach able to (i) virtually assess technical, economic and environmental performances of each fattened pig within a population; and (ii) help determine the pig characteristics resulting in contrasted environmental performances in a conventional system including feedstuffs classically used on French commercial farms. For that purpose, experimental data collected on 732 entire Large White males were used to adjust growth profiles using InraPorc® software and to estimate the amino acid (AA) requirements of pigs. Each individual profile was used to generate a virtual population of 1 000 pigs. For each population, technical performances were simulated with an individual-based model, economic and environmental evaluations were applied to these performances and then averaged to assess the individual performance of each of the 732 original pigs. Climate change, use of fossil resources, acidification, eutrophication potentials and land use impacts were evaluated per kg live BW at farm gate through life cycle assessment. A principal component analysis was applied to the correlation matrix between environmental and economic performances to identify their main drivers. Hierarchical clustering was used to group pigs with similar responses. Three clusters of pigs were distinguished. Cluster 1, with the best environmental and economic performances, combined low feed conversion ratios, relatively low-impact feeds and high protein deposition potential (PDm). Clusters 2 and 3 displayed the worst environmental performances. Cluster 3 had similar feed efficiency and economic performances as Cluster 1, but higher initial AA requirements, resulting in high-impact feeds and a lower protein deposition. Cluster 2 had the lowest-impact feeds due to the lowest initial AA requirements and were the least efficient. Feed efficiency, PDm and AA requirements of pigs at the beginning of fattening were the main factors affecting environmental performances. Contrary to previous studies where group feeding was modelled, we show that feed efficiency alone cannot be retained to identify pigs with the lowest impacts. Other pig characteristics such as AA requirements, PDm and environmental impacts should be accounted for to lower the environmental impacts of pig production.