Physiological, behavioral, and inflammatory responses of heat-stressed sows under fan and drip cooling systems during late gestation and lactation

Heat stress during late gestation and lactation compromises sow welfare, metabolic stability, and litter performance. This study evaluated the physiological, behavioral, and inflammatory responses of sows exposed to different cooling systems under elevated ambient temperature. Forty multiparous Landrace × Yorkshire sows (223.6 ± 25.8 kg) were assigned to a 2 × 2 factorial arrangement consisting of no cooling (CON), fan (FN), drip cooling (DC), and fan plus drip cooling (FN + DC). The average temperature–humidity index (THI) during the experimental period was 76, indicating heat stress condition. Cooling systems were associated with reductions in respiratory rate and rectal temperature during specific periods of late gestation (p < 0.05), with the more pronounced responses observed in FN + DC compared with CON. Hair cortisol concentrations were lower in FN and FN + DC than in CON (p < 0.05), whereas DC did not differ from CON. Behavioral indicators of thermal discomfort, including drinking frequency, standing time, and postural changes, were reduced in fan-based (p < 0.05), accompanied by increased lying behavior. Sow body weight, backfat thickness, feed intake, and reproductive parameters were not affected by treatments. However, fan-based cooling was associated with a higher number of weaned piglets and litter weight at weaning (p < 0.05). Among inflammatory markers, TNF-α concentration was reduced by fan-based systems (p < 0.05), whereas IL-1β and IL-6 concentrations were not affected. Overall, cooling systems, particularly fan-based strategies, were associated with improvements in selected physiological, behavioral, and productive indicators under heat stress conditions, although these responses were not consistent across all variables or time points.