Stereotypic behaviours in gestating sows - repetitive bar biting, rooting and vacuum chewing - are indicators of chronic frustration and poor welfare that are largely preventable.
Stereotypic behaviours in sows represent crystallised frustration - the outward expression of chronic welfare deprivation. They develop when motivated behaviours cannot be expressed and become self-reinforcing habits. Prevention through enrichment is far more effective than trying to reduce established stereotypies. This is one of the strongest arguments for providing rooting material and foraging opportunity from early in gestation.