Salivary stress biomarkers are increased, independently of maternal welfare status, in lactating Iberian piglets with lower postnatal growth

Abstract

Iberian pigs represent a small but economically significant segment of the Spanish swine sector, valued for the high quality of their products and the strong welfare-friendly image associated with their production systems. As management practices increasingly transition toward more intensive housing, reliable assessment of stress and welfare becomes essential. This study presents the first comprehensive characterization of salivary stress biomarkers—cortisol, α-amylase (sAA), butyrylcholinesterase (BChE), and total esterase activity (TEA)—in 68 Iberian sows across key reproductive stages (early, mid-, and late- gestation; mid-lactation; and weaning) and their relationship with piglet health and performance. Sows showed the highest biomarker levels early in gestation, with values decreasing as pregnancy and lactation progressed. Handling-intensive events elicited pronounced stress responses, especially in primiparous sows. No associations were detected between salivary biomarkers and sow body weight or back-fat depth. Piglets exhibited higher biomarker values at weaning than sows, reflecting acute handling stress. Sex and maternal parity did not significantly affect piglet biomarkers. Lower postnatal body weight was associated with elevated cortisol, sAA, and TEA, indicating increased physiological stress in lighter piglets. These findings validate salivary biomarkers as practical, non-invasive indicators of welfare in Iberian pigs and provide essential reference patterns to support improved management and welfare assessment in this breed