Pen Location Affects Thermoregulation and Feed Efficiency in Swine during Late Summer

The effects of pen location on swine thermoregulation and productivity were determined for 27 d during late summer. A total of 128 mixed sex pigs (¹/₂ Duroc x ¹/₄ Landrace x ¹/₄ Yorkshire) were randomly assigned to 16 pens in two grow-finish barns [n = 8 pens/barn; 57.4 ± 1.3 kg initial body weight (BW)]. Pen locations were pre-determined based on initial airflow (m/s) level [n = 4 high airflow (HAF) pens/barn and 4 low airflow (LAF) pens/barn]. High airflow and LAF pen locations were identical between each barn. Two sentinel gilts/pen were selected and vaginal temperature (T_V) was measured daily in 10 min intervals using thermochron temperature loggers. Additionally, whole body skin temperature (T_S) was measured with an infrared camera, and respiration rate (RR) was measured by counting flank movement of the sentinel gilts daily (0800h, 1500h). Pen airflow was measured daily (0800h, 1500h) with a vane anemometer. Ambient temperature (T_A) and relative humidity (RH) within each pen were recorded daily in 10 min intervals. Average daily gain (ADG) and average daily feed intake (ADFI) were determined bi-weekly. Data were analyzed using PROC MIXED in SAS 9.4. Although airflow was lower overall (P = 0.04; 11%) in LAF compared to HAF pens, no differences (P > 0.56) in T_A (27.63 ± 0.25⁰C; range 17.80-35.57⁰C) or RH (68.47 ± 0.46%; range 39.99-98.52%) were detected. An overall increase (P < 0.03) in T_V (0.23⁰C)_, minimum T_V (0.18⁰C), and maximum T_V (0.29⁰C) was detected in LAF versus HAF pens. Similarly, from 0800-1900h and 2000-0700h, T_V was greater overall (P < 0.02; 0.22 and 0.25⁰C, respectively) in LAF compared to HAF pens. A decrease in T_S (P = 0.04) was observed in LAF (37.39 ± 0.14⁰C) compared to HAF (37.61 ± 0.14⁰C) pens. No RR differences (P > 0.60; 76 ± 4 bpm) were detected with any comparison. While no ADG or ADFI differences were detected (P > 0.16; 0.75 ± 0.02 kg/d and 2.26 ± 0.07 kg/d, respectively), feed efficiency was decreased (P = 0.04; 6%) in LAF compared to HAF pens. No barn differences were detected with any comparison. In summary, pigs located in LAF pens had greater body temperature and reduced feed efficiency despite similarities in T_A and RH. These data have implications towards management of ventilations systems within swine facilities and the impact of pen-to-pen environmental variation on thermoregulation and productivity of pigs during hot summer months.