Influence of range of diurnal fluctuation of temperature on performance of growing pigs kept at an average ambient temperature of 24°C

The influence of the magnitude of variation of ambient temperature on the performance between 25 and 110 kg live weight was studied in two successive trials, each involving 192 crossbred gilts and barrows. Four treatments were compared: a constant temperature at 24°C or a fluctuating temperature according three diurnal kinetics, i.e. ±1.5, ±3.0 or ±4.5°C around 24°C. Minimal and maximum temperatures were reached at 0700 and 1900, respectively. A 12 h lighting schedule was adopted (0700-1900). Growth performance and feed consumption were measured. Feeding behaviour was also recorded in trial 2. Feed consumption was mainly diurnal as 80 % of total feed intake occurred during the day at 24 °C. This proportion decreased when variation of temperature increased (70 % at 24±4.5 °C) which resulted from a decreased feed intake level when temperature was above 24 °C during the day. Simultaneously, feed intake when temperature was below 24°C increased, especially during the night. However, this adaptation in feeding behaviour did not permit to maintain feed level which was lower when variation of temperature exceeded ±1.5 °C around 24°C (2.27 vs 2.17 kg/d at 24 and 24±4.5°C, respectively). Average daily gain was not affected by diurnal variation of temperature and averaged 885 g/d.