The social and feeding behaviour of growing pigs in deep-litter, large group housing systems

Two studies compared the social and feeding behaviour of Large White x Landrace entire male (non-castrated) growing pigs housed in deep-litter, large group and conventional housing systems. In Study 1, an ethogram of behaviour was developed. The pigs were housed at 1 m(2) per pig (200 pigs per pen) and 8.3 pigs per feeding space in the deep-litter system and 0.70 m(2) per pig (45 pigs per pen) and 8.5 pigs per feeding space in the conventional system. In Study 2, tile social and feeding behaviour of entire male growing pigs were compared. Eight hundred and eighty crossbred entire male pigs were used. There were 200 pigs per pen (1 m(2) per pig; 8.3 pigs per feeding space) in the deep-litter system and 20 pigs per pen (0.49 m(2) per pig; 10 pigs per feeding space) in the conventional system. When the average pig live weight was 60 kg, five non-focal pigs were removed from each pen resulting in 0.65 m(2) per pig (7.5 pigs per feeding space). In both studies, ad libitum feed was provided in double-spaced, wet-dry feeders. In each study there were four replicates, with 10 focal animals per treatment per replicate randomly selected for behaviour observations. All observations were conducted during day light. In Study 1, behaviour was observed when pigs were 21-22 weeks of age and in Study 2 social behaviour observations were conducted from 19 to 22 weeks of age, while feeding behaviour was observed from 20 to 22 weeks of age. Pigs housed in the deep-litter system spent more (P < 0.01) time standing and less (P < 0.05) time sitting and lying, and spent more (P < 0.001) time in locomotion compared to conventionally housed pigs. There was an increase (P < 0.05) in physical pen interactions and a higher (P < 0.001) incidence of social tactile interactions and agonistic (P < 0.001) and sexual behaviours (P < 0.01) in the deep-litter treatment. Such differences in social behaviour may be responsible for differences in growth performance commonly observed in deep-litter systems. Pigs in the deep-litter treatment spent less time (P < 0.05) within 1 m of the feeder, had fewer (P < 0.05) feeding events, had a longer (P < 0.05) duration of feeding and a lower (P < 0.05) frequency of social interactions around the feeder compared to pigs in the conventional treatment. The difficulties in gaining and maintaining access to the feeder in the conventional pens may be responsible for the shorter but more frequent feeding bouts observed. It is possible that the relatively unrestricted feeding that occurred in the deep-litter treatment may have resulted in increased fat deposition and poorer feed conversion efficiency, as observed in the industry setting, because of changes in feeding patterns that affect feed utilisation. (C) 2003 Elsevier Science B.V. All rights reserved.