Circularity and livestock diversity: Pathways to sustainability in intensive pig farming regions

CONTEXT: Intensive pig farming is challenged by high environmental impacts and dependence on outsourced inputs. Circular feeding strategies to improve nutrient cycling and livestock diversity have emerged as pathways to improve the sustainability. OBJECTIVE: This study explored the potential of increasing feed circularity and introducing sheep to improve the sustainability of a typical pig fattening region in the semiarid zone of Spain. METHODS: Three alternative circular scenarios were designed to relocate pig feed production while reintroducing sheep production. These scenarios were then compared to a business-as-usual (BAU) scenario. The feeding strategies scenarios differed in crude protein (CP) and in-feed amino acid (AA) supplementation for pigs (CircHigh, high CP with low AA; CircLow, low CP with high AA; CircNoAA, low CP without AA) and included grazing sheep to use crop residues, alfalfa and temporary vetch-oat pastures on fallow land. Yearly feed requirements for pigs were planned, and were met with cereal grains, oilseeds, legumes, rice bran and chopped alfalfa hay. Sheep carrying capacity was estimated from available forage sources. Indicators in five sustainability dimensions were considered: economic performance, landscape mosaic, livestock diversity, nitrogen (N) cycling, and feed-food competition. RESULTS AND CONCLUSIONS: Outsourced (BAU) pig feeding without sheep had low scores for indicators in all five dimensions. The feeding strategy for pigs strongly influenced the land area required to produce feed as well.

This study was conducted thanks to a Senior Researcher Mobility Grant from the Ministry of Universities of Spain (2022, PRX21/00146). The authors acknowledge funding from the ERA-NET project Mi Bicycle (Mitigation and adaptation through better biomass cycling in crop livestock systems of North and Western Europe) funded under the joint call ERA-NET Cofund SusAn, FACCE ERA-GAS, ICT-AGRI-FOOD and SusCrop.