Material consequences: An initial assessment of the influence of flooring type on lactating sow thermoregulation in summer heat

Abstract

Heat stress (HS) impairs lactating sows’ ability to provide adequate nutrition for their litters, prompting the development of management practices and new housing systems to alleviate its effects. However, few have investigated materials used in farrowing crate construction and their influence on sows’ ability to remain euthermic. Therefore, the study objective was to assess the association of metal (MTL) versus plastic (PLS) crate flooring with sow euthermia and litter performance under natural summer HS conditions. Landrace x Large White lactating sows and their litters (N = 23) were housed in individual crates in a single barn containing one room with MTL (n = 12) and one room with PLS (n = 11). Temperature and relative humidity were measured in 5 min intervals and were similar between the MTL (25.7 ± 1.8 °C and 88.0 ± 5.9%, respectively) and PLS (25.4 ± 1.9 °C and 86.2 ± 6.2%, respectively) rooms. All sows were provided ad libitum feed and water and piglets were cross fostered to standardize litter sizes (12.0 ± 1.4 piglets/litter). Sow vaginal temperature (TV) was assessed in 10 min intervals daily, and respiration rate [RR; breaths per minute (bpm)] and ear, shoulder, rump, and tail skin temperatures were measured at 0800, 1200, 1600, and 2000 h daily during the last 7 d of lactation. Sow average daily feed intake (ADFI) was measured weekly and litter weights were determined on d 1, 7, 14, and at weaning (d 19.7 ± 1.8). Piglet mortality was monitored starting at d 2 of lactation immediately post-crossfostering and continued throughout the trial. The sow was considered the experimental unit for sow-based measures, and litter was considered the experimental unit for litter-based measures. Parity was similar (P = 0.60) between MTL (2.25 ± 0.86) and PLS (2.88 ± 0.90) sows. Sow ADFI was increased (P < 0.01; 0.98 kg/d) for MTL versus PLS sows. Greater TV (P < 0.01; 0.08 °C) was detected for MTL versus PLS sows. Respiration rate was increased (P < 0.01; 10 bpm) at 2000 h for MTL versus PLS sows. Ear and shoulder skin temperatures were greater (P < 0.01; 0.34 and 0.65 °C, respectively) in MTL versus PLS sows. Average daily gain was similar (P = 0.55; 249.3 ± 11.6 g/d) for MTL and PLS litters. Mortality was greater overall (P < 0.01) for PLS (20.25 ± 5.14%) versus MTL (10.77 ± 5.44%) litters. In summary, MTL increased sow ADFI which may have influenced TV, RR, and skin temperatures, and was associated with lower pre-weaning mortality in litters.