3Pearce G P, Paterson A M. The effect of space restriction and provision of toys during rearing on the behaviour, prod uctivity and physioloogy of male pigs [J]. Appl Anim Behav Sci, 1993, 36: 11-28.
4Beattiea V E, Connell N E O', Moss B W. Influence of environmental enrichment on the behaviour, performance and meatquality of domestic pigs [J].Livestock Production Science, 2000, 65:71-79.
