Evaluation of sow thermal preference

Authors: ROBBINS, LINDSEY - Purdue University; GREEN, ANGELA - University Of Illinois; Lay Jr, Donald; Johnson, Jay; GASKILL, BRIANNA - Purdue University

Submitted to: International Society of Applied Ethology
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Despite advances in livestock cooling system technologies and management strategies, heat stress continues to negatively impact swine well-being, resulting in greater morbidity and mortality. The Federation of Animal Science Societies (Ag Guide) states that the thermal comfort zone (TCZ) for any pig over 100 kg is between 10-25°C. These guidelines are dated and do not reflect the increased heat generation in current genetic lines. We hypothesized that sows have a lower TCZ than what is stated by the Ag Guide and this will be altered by gestational stage and parity. The thermal preference of 21 sows was tested in a factorial design of parity (2, 3, and 5) and gestational stage: open (not pregnant, n=7), mid-gestation (45-65 days pregnant, n=7) or late gestation (95-108 days pregnant, n=7). Each individual sow was placed within a thermal gradient (10°C to 31°C) and acclimated to the environment for 24 h prior to testing. During the following 24 h testing period, sows were continuously videotaped. The location, behavior (active, inactive, or other) was documented using instantaneous scan samples every 10 minutes. Data was analyzed using a GLM and was Log10 transformed for normality. Tukey tests and bonferroni corrected custom tests were used for post hoc comparisons. Peak temperature preference was determined by the maximum amount of time spent at a specific temperature, and preference range was the LSM±SE from the peak temperature. Parity did not affect thermal preference (F2,339 = 2.66, P=0.07). The amount of time spent in different temperatures was altered by behavior (F1,339 = 34.48, P<0.01) and gestational stage (F2,339 = 7.43, P<0.01). Overall, sows were inactive and spent the most time at 14.8°C. While inactive, sows had a thermal preference range between 14.0-15.8°C and during active behaviors thermal preference ranged between 12.8-16.0°C. Differences between peak preference temperatures were observed between late gestation (14.4°C) and mid-gestation (15.0°C; F1,339 = 13.68, P<0.01) and open sows (14.8°C; F1,339 = 8.07, P<0.01). However, no differences were found between mid-gestation and open sows (F1,339 = 0.97, P=0.33). Thermal preference for open and mid-gestation sows were similar, ranging between 13.6-16.4°C. Late gestation sows had a thermal preference between 13.0-15.6°C. Furthermore, late gestation sows spent the least amount of time between 27-30°C compared to open and mid gestation sows (tukey: P<0.01). The thermal preference range for sows tested in this study fell within recommendations by the Ag. Guide (10-25°C); however, sows in the present study preferred a much narrower range of temperatures (13.0-16.4°C). This study indicates that the TCZ of sows is affected by gestational stage and behavior indicating that the Ag Guide may require updating based on this information.