PS4-1. Material Consequences: Flooring Type Modulates Sow Thermoregulation and Litter Survival in Summer Heat

Physiological changes resulting from heat stress (HS) such as reduced feed intake, blood flow, nutrient partitioning, and hyperthermia, impair 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 impact of metal (MTL) versus plastic (PLS) crate flooring on sows’ ability to remain euthermic and the downstream impacts on litter performance under natural summer HS conditions. In total, 23 Landrace x Large White lactating sows and their litters were housed in individual crates in a single barn containing one room with MTL (n = 12; parity = 2.23 ± 2.43) and one room with PLS (n = 11; parity = 2.88 ± 3.19). Throughout the trial, temperature and relative humidity were measured in 5 min intervals and were similar between the MTL (25.70 ± 1.80 °C and 88.00 ± 5.90%, respectively) and PLS (25.40 ± 1.90 °C and 86.20 ± 6.20%, respectively) rooms. All sows received ad libitum access to feed and water and piglets were cross fostered to standardize litter sizes across treatments (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 feed intake (FI) was measured daily and litter weights were determined on d 1, 7, 14, and at weaning (d 19.7 ± 1.8). Piglet mortality was monitored throughout the trial. Data were analyzed using PROC GLIMMIX and sow was considered the experimental unit for sow-based measures, and litter was considered the experimental unit for litter-based measures. Feed intake was increased (P < 0.01; 0.98 kg/d) for MTL versus PLS sows. Vaginal temperature was greater overall (P < 0.01; 0.10 °C) 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) for MTL versus PLS sows. Average daily gain was similar (P < 0.40; 249.3 ± 11.6 g/d) for MTL and PLS litters. Mortality was greater (P < 0.01) for PLS (25.2 ± 3.9%) versus MTL (13.8 ± 4.1%) litters. In summary, MTL increased sow FI which likely influenced TV and RR responses. Despite this, no improvements in litter growth were observed, but an increase in piglet mortality may preclude the use of PLS in farrowing crate construction.