Methods for evaluation of the thermal environment in the animal occupied zone for weaned piglets

Two evaluation methods are introduced for expression of the quality of the thermal conditions in the animal-occupied zone (AOZ) in rooms for weaned piglets. One method uses only the AOZ temperature, while the other uses the kata-value (KV), which combines air velocity and temperature and indicates the heat loss to the environment. AOZ thermal conditions should be within the thermo-neutral zone (TNZ) of the piglets. The methods use two new numerical indicators, based on the duration and the magnitude of excess of AOZ thermal conditions outside the TNZ: one referring to the number of degree-hours (°Ch), and the other to the number of kata-value-hours (KVh) during a batch. The objective was to evaluate the two methods in a door-ventilated room for weaned piglets. In the experiment, temperature was measured in all ten pens of a room and air velocity in three pens during eight successive batches, together lasting about one year. Pens closer to the air inlet had higher temperatures and lower KV than pens in the back of the room. Momentary temperature difference between pens reached up to 7°C. During the first days of most batches, pen conditions in the back of the room were "too cold." At the end of most batches, pen conditions in the middle of the room were "too warm." The value of the two indicators varied per pen and per batch from 0 to 319°Ch (0 to 219 KVh) "too cold" and from 0 to 602°Ch (0 to 793 KVh) "too warm." For "too warm" conditions, there was a significant (P <0.001) and strong correlation between the two indicators (R2 > 0.96), but not for "too cold" conditions (R 2 > 0.48). Therefore, measuring air velocity in addition to temperature in the AOZ for recognition of "too cold" conditions had surplus value. Excluding outliers from one extremely warm batch, the maximum value of the indicator for "too warm" was 65°Ch. This indicator significantly affected the feed conversion ratio, which increased with 0.0024 kg/kg per °Ch, and daily growth and daily feed intake, which decreased with 0.0022 kg/animal and 0.0030 kg/animal, respectively, per °Ch. The methods presented are useful tools in the technical evaluation of climate systems and for a more optimal climate control in the AOZ.