Effect of individual housing on the feeding behaviour of previously group housed growing pigs

The feeding behaviour of individually housed growing pigs differs significantly from that of group housed animals, with individual penning resulting in shorter, more frequent visits to the feeding trough (De Haer and Merks, 1992. Anim. Prod., 54: 95-104). Substituting group housing by a single housing environment was therefore expected to increase substantially the number of visits to the feeding trough. Three groups of ten cross-bred entire male pigs (initial live-weight 29.3 +/- 0.6 kg; mean +/- SE) were housed for 14 days (Period 1) with ad libitum access to one computerized single-space feeder per group. Four pigs were chosen from each group; two pigs showing a high feeding frequency (It pigs: 18.9 +/- 2.0 visits day(-1); mean +/- SE; n = 6) and two pigs showing a low feeding frequency (L pigs: 9.5 +/- 0.8 visits day(-1); mean +/- s.e.; n = 6). The L pigs had a higher feed intake per visit (137 vs 82 g per visit; SED = 8; P < 0.001), acid a lower daily feed intake (1246 vs 1477 g day(-1); SED = 84; P < 0.05) than H pigs, On Day 15, H and L pigs were moved to individual pens identical to the group pens for a period of 14 days (Period 2). This individual housing resulted in only a small increase in the frequency of feeder visits (2.8 +/- 0.8 visits day(-1)), irrespective of the feeding frequency displayed by the pigs during Period 1. The relatively small increase in number of daily feeder visits resulted in a significant increase (P < 0.05) in daily feed intake, leading to no differences between pigs in daily feed intake once individually penned, Pigs showing a low number of daily feeder visits when group housed may have been constrained in terms of daily feed intake as a result of the displayed feeding pattern. In addition, the feeding pattern of growing pigs may be less flexible than expected, and pigs, which have been constrained in their food intake, will make only small modifications to their feeding pattern, sufficient to compensate for the previous constraint. It is likely that growing pigs will adhere to a feeding pattern that has provided them with sufficient food in the past, even when a change in the environment allows for more extreme modifications to occur.