[Arey D. S. (1993). The effect of bedding on the behaviour and welfare of pigs. Anim. Welfare, 2: 235-246.]Search in Google Scholar
[Arey D. S., Franklin M. F. (1995). Effects of straw and unfamiliarity on fighting between newly mixed growing pigs. Appl. Anim. Behav. Sci., 45: 23-30.]Search in Google Scholar
[Beattie V. E., O'Connell N. E., Moss B. W. (2000). Influence of environmental enrichment on the behaviour, performance and meat quality of domestic pigs. Livest. Prod. Sci., 65: 71-79.]Search in Google Scholar
[Beattie V. E., Walker N., Sneddon I. A. (1995). Effects of environmental enrichment on behavior and productivity of growing pigs. Anim. Welfare., 4: 207-220.]Search in Google Scholar
[Blackshaw J. K., Thomas F. J., Lee J. A. (1997). The effect of a fixed or free toy on the growth rate and aggressive behavior of weaned pigs and the influence of hierarchy on initial investigation of the toys. Appl. Anim. Behav. Sci., 53: 203-212.]Search in Google Scholar
[Commission Directive 2001/93/EC of 9 November 2001 amending Directive 91/630 EEC laying down minimum standards for the protection of pigs (2001), Official Journal of the European Community, 1.12.2001.]Search in Google Scholar
[Croney C. C., Adams K. M., Washington C. G., Stricklin W. R. (2003). A note on visual, olfactory and spatial cue use in foraging behaviour of pigs: Indirectly assessing cognitive abilities. Appl. Anim. Behav. Sci., 83: 303-308.]Search in Google Scholar
[Day J. E. L., Spoolder H. A. M., Burfoot A., Chamberlain H. L., Edwards S. A. (2002). The separate and interactive effects of handling and environmental enrichment on the behaviour and welfare of growing pigs. Appl. Anim. Behav. Sci., 75: 177-192.]Search in Google Scholar
[Day J. E. L., Spoolder H. A. M., Edwards S. A. (2001). Straw as environmental enrichment: which properties do growing pigs find behaviourally rewarding? Proc. International Symposium of the C. I. G. R. Animal Welfare Considerations in Livestock Housing Systems, 2nd Technical Section, pp. 157-167.]Search in Google Scholar
[Fraser D. (1984). The role of behaviour in swine production: a review of research. Appl. Anim. Ethol., 11: 317-339.]Search in Google Scholar
[Fraser D., Phillips P. A., Thompson B. K., Tennessen T. (1991). Effects of straw on the behavior of growing pigs. Appl. Anim. Behav. Sci., 30: 307-318.]Search in Google Scholar
[Hafez E. S. E. (1975). Editor. The behaviour of domestic animals. Bailliere-Tindall, London, p. 301.]Search in Google Scholar
[Hendriks H. J. M., Pedersen B. K., Vermeer H. M., Wittmann M. (1998). Pig housing systems in Europe: Current distributions and trends. Pig News Inform., 19: 97N-104N.]Search in Google Scholar
[Jones J. B., Wathes C. M., White R. P., Jones R. B. (2000). Do pigs find a familiar odorant attractive in novel surroundings? Appl. Anim. Beh. Sci., 70: 115-126.]Search in Google Scholar
[Keeling L. J., Gonyou H. W. (2001). Social behaviour in farm animals. CAB International, pp. 147-157.10.1079/9780851993973.0000]Search in Google Scholar
[Kelly H. R. C., Bruce J. M., English P. R., Fowler V. R., Edwards S. A. (2000). Behaviour of 3-week weaned pigs in Straw-Flow, deep straw and flat-deck housing systems. Appl. Anim. Behav. Sci., 68: 269-280.]Search in Google Scholar
[Lyons C. A. P., Bruce J. M., Fowler V. R., English P. R. (1995). A comparison of productivity and welfare of growing pigs in four intensive systems. Livest. Prod. Sci., 43: 265-274.]Search in Google Scholar
[Meese G. B., Conner D. J., Baldwin B. A. (1975). Ability of the pig to distinguish between conspecific urine samples using olfaction. Physiol. Behav., 15: 121-125.]Search in Google Scholar
[Mench J. A. (1998). Environmental enrichment and the importance of exploratory behaviour. In: Second Nature: Environmental Enrichment for Captive Animals, Sheperdon D. J., Mellen, J. D., Hutchins M. (Eds.). Smithsonian Institution Press, Washington, DC, pp. 30-46.]Search in Google Scholar
[Merlot E., Meunier-Salaün M. C., Prunier A. (2004). Behavioral, endocrine and immune consequences of mixing in weaned piglets. Appl. Anim. Beh. Sci., 85: 247-257.]Search in Google Scholar
[Newberry R.C (1995). Environmental enrichment: increasing the biological relevance of captive environments. Appl. Anim. Behav. Sci., 44: 229-243.]Search in Google Scholar
[Nowicki J., Kopyra M., Klocek C. (2007). The behavioural reaction of weaners to hanging toys: wooden ball and aromatized wooden ball - way to reduce aggression after mixing. J. Cent. Eur. Agri., 4: 447-452.]Search in Google Scholar
[Pearce G. P., Paterson A. M. (1993). The effect of space restriction and provision of toys during rearing on the behaviour, productivity and physiology of male pigs. Appl. Anim. Behav. Sci., 36: 11-28.]Search in Google Scholar
[Pearce G. P., Paterson A. M., Pearce A. N. (1989). The influence of pleasant and unpleasant handling and the provision of toys on the growth and behaviour of male pigs. Appl. Anim. Behav. Sci., 23: 27-37.]Search in Google Scholar
[Petersen V. (1994). The development of feeding and investigatory behaviour in free-ranging domestic pigs during their first 18 weeks of life. Appl. Anim. Behav. Sci., 42: 87-98.]Search in Google Scholar
[Petersen V., Simonsen H. B., Lawson L. G. (1995). The effect of environmental stimulation on the development of behaviour in pigs. Appl. Anim. Behav. Sci., 45: 215-224.]Search in Google Scholar
[Ruiterkamp W. A. (1987). The behaviour of grower pigs in relation to housing systems. Neth. J. Agric. Sci., 35: 67-70.]Search in Google Scholar
[Scott K., Taylor L., Gill B. P., Edwards S. A. (2006). Influence of different types of environmental enrichment on the behaviour of finishing pigs in two different housing systems. 1. Hanging toy versus rootable substrate. Appl. Anim. Behav. Sci., 99: 222-229.]Search in Google Scholar
[Van de Weerd H. A., Docking C. M., Day J. E. L., Avery P. J., Edwards S. A. (2003). A systematic approach towards developing environmental enrichment for pigs. Appl. Anim. Behav. Sci., 84: 101-118.]Search in Google Scholar
[Van de Weerd H. A., Docking C. M., Day J. E. L., Breuer K., Edwards S. A. (2006). Effects of species relevant environmental enrichment on the behaviour and productivity of finishing pigs. Appl. Anim. Behav. Sci., 99: 230-247.]Search in Google Scholar
[Van de Weerd H. A., Docking C. M., Day J. E. L., Edwards S. A. (2005). The development of harmful social behaviour in pigs with intact tails and different enrichment backgrounds in two housing systems. Anim. Sci., 80: 289-298.]Search in Google Scholar
[Young R. J., Carruthers J., Lawrence A. B. (1994). The effect of a foraging device (The ‘Edinburgh Football’) on the behaviour of pigs. Appl. Anim. Behav. Sci., 39: 237-247.]Search in Google Scholar