The farrowing period — when sows give birth and nurse piglets — involves some of the most complex behaviours in pig production and raises fundamental welfare questions about the systems used to manage it. Understanding sow maternal behaviour is essential for improving welfare in pig production.
In naturalistic conditions, sows build elaborate nests 24-48 hours before farrowing, selecting sheltered sites and gathering materials. Nest building is a strongly motivated behaviour — sows will work intensively for nesting material even when other resources are abundant. Deprivation of nest-building opportunity causes significant frustration and stress.
After farrowing, sows show complex maternal behaviours: maintaining contact with piglets, positioning carefully to allow nursing, responding to piglet distress calls, and protecting the litter. These behaviours require freedom of movement to express.
Conventional farrowing crates confine sows in metal cages barely larger than the sow herself, preventing turning around for the entire farrowing and lactation period (3-5 weeks). This completely prevents nest building and severely restricts maternal behaviour. The welfare compromise is substantial:
The primary justification for farrowing crates is piglet mortality prevention — piglets are easily crushed (overlaid) by sows, particularly in the first days after birth. Overlying accounts for 50-60% of pre-weaning piglet mortality in non-crate systems. This represents a genuine welfare conflict between sow and piglet welfare.
Free-farrowing systems — including the PigSAFE pen, Comfort system, and various nest-box designs — aim to maintain piglet survival while allowing sow freedom of movement. Well-designed loose systems achieve comparable piglet survival to crates when combined with good management, genetic selection for maternal ability, and adequate supervision at farrowing.
Some systems use temporary confinement — allowing sows freedom of movement before and after the critical crushing-risk period (first 3-5 days), with brief confinement only during highest-risk periods. This compromise approach is gaining commercial adoption in several countries.
Denmark has banned conventional farrowing crates from 2035. New Zealand banned them by 2023. The UK and Germany are reviewing crate regulations. As welfare science and loose-farrowing system design continue to improve, legislative transition away from crates is expected to accelerate globally.