Determining the optimal macroenvironment temperature to house lactating sows and their litters.

To accommodate piglet thermal requirements, producers use heating lamps or pads combined with maintaining farrowing room macroenvironment dry bulb temperatures (MTDB) at levels approaching heat stress for lactating sows. However, this may decrease sow feed consumption, milk production, and litter growth. Therefore, the study objective was to determine the MTDB that would improve sow and litter productivity and welfare measures. Lactating sows (N = 37; Landrace × Yorkshire; parity = 3.1 ± 1.7) and their litters (12.0 ± 1.0 piglets/litter) were housed in 1 of 3 farrowing room MTDB: LOW (n = 12 sows and litters; 15.0 ± 0.4 °C), MID (n = 13 sows and litters; 19.3 ± 0.2 °C), and HIGH (n = 12 sows and litters; 24.6 ± 0.8 °C). Lactating sows and litters were on trial from farrowing to weaning (day 19.8 ± 0.9 of age). Thermocouples were used to record individual farrowing crate MTDB, and piglets were provided a 0.34 × 1.52 m heating pad set to 35.0 °C. Piglets were individually weighed on days 1, 7, 14, and at weaning to determine average daily gain (ADG). Sow feed intake (FI) was recorded daily. Sow and piglet respiration rates [RR; breaths per minute (bpm)] and skin temperature were measured at 0800, 1200, 1600, and 2000 hours daily, and sow vaginal temperature (Tv) was measured in 10-min intervals. Core body temperature (Tc) was recorded on 1 piglet/litter in 10-min intervals using implanted loggers. Milk samples were collected on lactation days 6, 12, and 18. Data were analyzed using PROC GLIMMIX with either sow or litter as the experimental unit. Sow FI was greater (P < 0.01; +1.25 kg) for LOW and MID versus HIGH sows, but similar for LOW and MID sows. Piglet ADG was greater overall (P < 0.01; +45 g/d) for LOW and MID versus HIGH piglets, but similar for LOW and MID piglets. Sow RR was greater (P < 0.01; +18 bpm) for HIGH versus MID and LOW sows, but were similar for MID and LOW sows. Piglet Tc was reduced (P < 0.01; -0.25 °C) in HIGH versus MID and LOW litters but was similar for MID and LOW litters. Milk fat was reduced (P = 0.02; 1.2%) for LOW versus MID sows on d 12, but similar versus HIGH sows. Sow FI was maximized (quadratic; P < 0.01) at 17.2 °C. Piglet ADG and Tc were decreased (cubic; P < 0.01) and sow Tv was increased (cubic; P < 0.01) at 17.0, 18.9, and 20.9 °C, respectively. These data suggest that farrowing room MTDB between 17.0 and 21.0 °C combined with a piglet heating pad may maximize both sow and litter productivity and welfare measures.