Sows have a powerful pre-farrowing nesting motivation that is almost universally frustrated in industrial systems, causing significant psychological distress and affecting maternal behavior.
Nesting motivation in sows is among the most compelling examples of animal motivation research applied to welfare. The drive to build a nest before farrowing is so strong that sows deprived of materials show the same behavioral urgency as motivated animals given full access — they simply cannot complete the behavior. This frustrated motivation causes distress measurable in behavioral and physiological terms. The transition from farrowing crates to free-farrowing systems is technically challenging — piglet crushing rates can rise — but research shows good management can achieve comparable piglet mortality with dramatically improved sow welfare. Countries like Sweden have demonstrated this is feasible at scale.