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 as N cycling. Only the CircLow scenario could feed the current pig stocks in the region with the arable land available. The CircHigh strategy combined with grazing sheep scored highest for most of the dimensions, except for feed-food competition indicators. The CircLow strategy had good scores for most of the dimensions, except for N cycling indicators, whose scores decreased due to the lower N content of slurry. The CircNoAA strategy increased the use of rice bran as a food coproduct and decreased N surplus, but also impaired the economic performance (land productivity and feeding costs). Although the CircLow strategy required less land area to grow legumes, it resulted in a slightly higher crop diversity and a higher sheep carrying capacity when sowing temporary pastures. SIGNIFICANCE: N cycling and overall sustainability of regions with intensive livestock production was improved through feed circularity, that included reducing CP with high in-feed AA, and livestock diversity, by reintroducing sheep as complementary livestock that can graze crop residues and temporary pastures. These results may help to inform future rural policies to help upscale more sustainable practices in intensive pig farming regions.