The effect of restricting pen space and feeder availability on the behaviour and growth performance of entire male growing pigs in a deep-litter, large group housing system

Recent research has shown that pigs housed in large groups on deep-litter have longer feeding events with less disruption from other pigs compared to pigs maintained in conventional housing systems. It has been speculated that this change in feeding behaviour is associated with increased fat deposition and feed conversion ratio. An experiment was designed to examine the effect of different pen space allowance and feeder availability on the behaviour and growth performance of growing pigs in a deep-litter, large group system. A 2 x 2 factorial experiment examined the effects of pen space and feeder space from 10 to 23 weeks of age, using 2460 crossbred (Large White x Landrace) entire male (non-castrated) pigs. Pen space was either "unrestricted" (0.88 m(2) per pig) or "restricted" (0.45-0.74 m(2) per pig) and feeder space was either "unrestricted" (9 pigs per feeding space) or "restricted" (15 pigs per feeding space). There were 12 pens of pigs, each with a group size of 205 pigs and pelleted feed was offered ad libitum using double spaced, wet-dry feeders (41 cm wide feeding space). The four treatments were replicated three times and 10 animals per treatment per replicate were selected at random as focal animals for behaviour observations. Feeding behaviour was observed between 5:30 and 19:00 h using time-lapse video for 1 week at 10, 17 and 23 weeks of age. Treatment effects were analyzed using analysis of variance with the group used as the experimental unit. Reducing pen space reduced (P < 0.01) carcass backfat. This effect appears unrelated to feeding behaviour since pen space did not affect feeding behaviour. Reducing feeder space increased (P < 0.05) the average duration of feeding events and increased (P < 0.05) the feed conversion ratio, which may be the result of feed wastage. There was no evidence to support the hypothesis that reducing either pen or feeder space produces shorter, more frequent feeding events. In conclusion, reduced backfat when pen space was reduced was not associated with changes in feeding behaviour but social stress resulting from reduced pen space may be implicated. Further research on the effects of stress physiology on growth performance is required. (C) 2003 Elsevier B.V. All rights reserved.