2002 ASAS Annual Meeting Abstract

Heat Stress in the Outdoor Lactating Sow: Influence of Shaded Wallows on Behavior, Performance and Physiology. Anna K. Johnson¹*, Frank M. Mitlöhner¹*, Julie L. Morrow², and John J. McGlone¹. ¹Pork Industry Institute and ²USDA-ARS, Texas Tech University, Lubbock, 79409, USA.

One hundred ten PIC USA sows and their litters were used to determine the effects of shaded (SH N=53) versus unshaded wallows (CO N=57) on sow behavior, performance and physiology. Sows ranged over five parities and were fed a completely balanced diet. Behavior data were collected by 15 min scan samples, over a 24h period/wk for 15wk. All sows were observed twice when litter age was 5 and 15 d respectively. Duration of standing, lying, walking, feeding, inactive, head down, drinking and location within the radial did not differ (P > 0.05) for wallow treatments. Performance parameters were collected from the farrowing records but there were no (P > 0.05) differences for wallow treatments or temperature by wallow treatment interactions. Respiration rates (RR) breathes/min were collected on 49 sows over 7 wk when maximum air temperatures exceeded 32^oC. Wallow treatments did not (P > 0.05) affect RR rates but there was a wallow treatment by temperature interaction for CO sows which had a higher (P=0.006) RR compared to SH sows. Blood was collected from the sow on the d of weaning. Physiological parameters measured were total white blood cells counts, differentials, acute phase proteins, neutrophil chemotaxis and chemokinesis, and packed cell volume. There were no (P > 0.05) differences for wallow treatments for most physiological measures. However, treatments had a differential (P < 0.05) response over air temperature for total WBC counts (10³/µL), % lymphocytes, neutrophil:lymphocyte ratio, %, eosinophils, and chemokinesis. In conclusion, sows spent large percentages of their daily time budget inside the farrowing hut and little time at the wallow during warm weather. Shading the wallow did not result in improved wallow use or litter performance. While differences were seen in physiological measures all values were within normal physiological ranges for lactating sows indicating that these sows were adapting equally well to the shaded and unshaded wallows.

Key Words: Behavior, Heat Stress, Performance, Physiology, Sows