Reverse heating system for chilling pigs in summertime

Climatic inadequacies may affect welfare and performance of pigs. The aim of this study was to evaluate the potential of running the heating system backwards during the summer with the aim to accomplish a more comfortable indoor climate.

The study was made in herd with a module stable for fatteners with a natural mechanic ventilation system. Each unit had two pens sized 19.6 m², out of which 5.7 m² was a dunging area located outdoors. Each pen housed 20 pigs (0.98 m² per pig). Pigs entered the stable at 12 weeks of age and were reared to market weight all in-all out.

Summer batches from two years were compared. A heat exchanger with a high effect (Alfa Laval 70 kW; ∆t = 10 °C) was installed and connected to the water-based heating system of floors, running from the 28th of May in 2013 and from the 22nd of April in 2014. The water-flow capacity was 3 m³/day in 2013 and 15 m³/day in 2014. Temperature and relative air humidity were monitored and Temperature-Humidity Indexes (THI) were established.

Four pens were videotaped every Tuesday during the entire fattening period. The photos at 08.00 and at 16.00 were used to count the number of pigs at the lying area. They were also used to score the level of contamination of the lying area (0=clean, 1= dung / urine in > 25% of the pen, 2= < 50%, 3 = > 50%).

The summer 2013 was colder, but the mean temperature outdoors (20.2±3.1 vs. 21.6±6.0) and indoors (2013, 23.6±1.7 vs. 24.8±2.5) ranged within 1.5°C. Still, the mean floor temperature was 1°C lower in 2014 (25.2±1.0 vs. 26.3±0.8). The lying area was cleaner in 2014 than in 2013 (P< 0.001; both am and pm).

The mean indoor temperatures were constantly 1°C higher in the late afternoon. Thus, also the highest THI-values were recorded in the afternoons. Still, the lying area were cleaner in the afternoon than in the morning during both years (2013, 0.57±0.7 vs. 1.23±1.0, P< 0.001; 2014; 0.13±0.3 vs. 0.32±0.6, P< 0.05). In 2014, more pigs were at the lying area, both at morning (3.0±1.6 vs. 2.3±2.4, P=0.01) and afternoon (4.4±2.3 vs. 3.7±2.8, P< 0.001).

Growing pigs prefer chill during warm summer days. An effective chilling floor effectively improved the pen hygiene as more pigs used the lying area instead of the slatted dunging area for resting. They thereby avoided the dunging area with the aim to search chill from manure and urine when resting.

Disclosure of Interest: None Declared.