Voluntary feed intake and feeding behaviour of group-housed growing pigs are affected by ambient temperature and body weight

The effect of ambient temperature on individual feeding behaviour was studied in six groups of Pietrain x Large White barrows. In experiment 1 (two groups), ambient temperature varied in a cyclic way from 22 to 12 degrees C and 12 to 22 degrees C with three or four consecutive days at each of the following temperatures: 22, 19, 16, 14 or 12 degrees C. Similarly, in experiment 2 (two groups), temperature varied from 19 to 29 degrees C and 29 to 19 degrees C with three or four consecutive days at 19, 22, 25, 27 or 29 degrees C. In both experiments, each group was used over two successive cycles with an initial body weight (BW) of 37 kg at cycle 1 (four pigs per group) and 63 kg at cycle 2 (three pigs per group). During experiment 3, groups of four pigs were exposed to varying temperatures over one cycle either as in experiment 1 (one group) or as in experiment 2 (one group); their initial BW was 45 kg. Photoperiod was fixed to 12 h of light. In experiments 1 and 2, neither the daily number of meals (II) nor the rate of feed intake (37 g/min) were affected by temperature. The daily number of meals was lower at cycle 2 (9 vs. 12 at cycle 1 on average) but their size was higher (305 vs. 181 g/meal at cycle 1). The feeding pattern was mainly diurnal (63%). From individual data obtained at each temperature level and each stage of growth in this study (N = 296), an equation to predict the voluntary feed intake (VFI) from temperature (T, ranging between 12 and 29 degrees C) and body weight (BW, ranging between 30 and 90 kg) is proposed: VFI (g/d) = - 1264 + 117T - 2.40T(2) + 73.6BW - 0.26BW(2) - 0.95T X BW (RSD = 329). The present relationship indicates that VFI depends on temperature and body weight with a marked negative effect of high ambient temperatures in heavier pigs. (C) 2000 Elsevier Science BN. All rights reserved.