Efficient pigs, those that grow quickly with little feed, are often considered the most environmentally friendly because they use fewer resources. Yet efficiency does not always align with sustainability.
A joint study by two teams, at UMR Pegase and UMR GenPhySE of INRAE, shows that efficient animals can have greater negative environmental impacts than their slower-growing counterparts.
Pig farming is often criticized for greenhouse gas emissions, fossil fuel use, and water pollution caused by nitrogen and phosphorus emissions. These concerns drive efforts to reduce the industry’s footprint.
In Europe, concentrated livestock farming in certain regions contributes to coastal and groundwater eutrophication. In France, as elsewhere, reducing pig farming’s environmental footprint has become a central objective.
Feed production and individual needs
The industry now focuses on reducing the consumption index, such as increasing the capacity of an animal to convert feed into meat, to reduce these impacts. Feed production accounts for most impacts in conventional systems.
Previous studies have assessed impacts at the group level, assuming that all pigs consume the same feed adapted to an ‘average individual’. This overlooked individual nutritional variability.
In reality, each pig has specific energy and amino acid requirements. Ignoring these differences affects feed consumption, growth, and waste, leading to inaccurate assessments of environmental impact.
A virtual farm experiment
To address this, Pegase researchers designed a model simulating individual technical and environmental performance. Using data collected from 732 pigs, they created 732 virtual populations of 1000 animals, each with the average performance of one of the experimental pigs.
Based on InraPorc software, the simulation model calculated the precise nutritional needs for each pig and simulated feed compositions best suited to those requirements.
This allowed the researchers to evaluate the zootechnical, environmental, and economic (profitability) performance associated with this type of animal husbandry. Impacts on climate change, fossil fuel use, soil acidification, water eutrophication potential, and land use were assessed using life cycle analysis and expressed per kg of live weight at the farm.
This ‘individualized’ approach makes it possible to assess how specific traits—such as protein deposition potential or amino acid needs at the start of growth—shape the environmental, technical and economic performance of each animal.
Three pig profiles and unexpected results
Researchers identified three distinct pig profiles:
- ✅ ‘Balanced’ pigs: Efficient throughout growth, with moderate feed consumption and a feed composition that has a reduced environmental impact. They perform best economically and environmentally.
- ✅ ‘Economical’ pigs: Low nutritional requirements per kg of feed at the start of fattening and low-polluting feed, but slower growth than the other two profiles. Their lower efficiency leads to an increase in impacts per kg of meat, as their total feed consumption is higher.
- ✅ ‘Demanding’ pigs: Very efficient at growing quickly early in fattening, but their high amino acid requirements necessitate feed rich in soya or sunflower. This feed is costly and environmentally damaging.
Not all of the most efficient pigs (‘balanced’ and ‘demanding’) are necessarily suited to sustainable farming. Fast-growing animals often require protein-rich feeds, often made with imported ingredients, which increase emissions and environmental costs.
A sustainable pig is therefore a ‘balanced’ pig, efficient with stable growth potential throughout the fattening period. It is also a pig fed according to its actual needs, with feed adapted to both its metabolism and the environment. Adapting the diet to each individual could reduce nitrogen emissions and overall emissions.
This study reveals that economic performance and environmental performance do not always coincide. However, compromises are possible when accounting for diverse animal profiles.
The future of sustainable livestock farming will involve evaluating each animal’s economic and environmental performance, both in terms of selection and feed. Moving beyond yield-based approaches, the industry must balance zootechnical, environmental, and economic performance.