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The prevention and control of feather pecking: application tocommercial systems

Published online by Cambridge University Press:  13 December 2013

C.J. NICOL ,
M. BESTMAN ,
A-M. GILANI ,
E.N. DE HAAS ,
I.C. DE JONG ,
S. LAMBTON ,
J.P. WAGENAAR ,
C.A. WEEKS  and
T.B. RODENBURG
C.J. NICOL*
Affiliation:
Animal Welfare & Behaviour Group, School of Veterinary Sciences, Bristol University, Langford House, Langford, Bristol, BS40 5DU, United Kingdom
M. BESTMAN
Affiliation:
Louis Bolk Institute, Hoofdstraat 24, 3972 LA Driebergen, The Netherlands
A-M. GILANI
Affiliation:
Animal Welfare & Behaviour Group, School of Veterinary Sciences, Bristol University, Langford House, Langford, Bristol, BS40 5DU, United Kingdom
E.N. DE HAAS
Affiliation:
Adaptation Physiology Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
I.C. DE JONG
Affiliation:
Livestock Research, Wageningen UR, PO Box 65, 8200 AB, Lelystad, The Netherlands
S. LAMBTON
Affiliation:
Animal Welfare & Behaviour Group, School of Veterinary Sciences, Bristol University, Langford House, Langford, Bristol, BS40 5DU, United Kingdom
J.P. WAGENAAR
Affiliation:
Louis Bolk Institute, Hoofdstraat 24, 3972 LA Driebergen, The Netherlands
C.A. WEEKS
Affiliation:
Animal Welfare & Behaviour Group, School of Veterinary Sciences, Bristol University, Langford House, Langford, Bristol, BS40 5DU, United Kingdom
T.B. RODENBURG
Affiliation:
Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands Behavioural Ecology Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
*
Corresponding author: c.j.nicol@bris.ac.uk
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Abstract

Studies on the prevalence of feather pecking in different commercial laying hensystems and its welfare and economic impacts are reviewed in the followingpaper. Current methods for controlling feather pecking include beak-trimming andalterations to light regimes, but these methods have significant disadvantagesfrom the perspective of bird welfare. A substantial body of research has nowidentified risk factors for feather pecking during both the rearing and layingperiods. It is argued that these findings can be translated into optimisedmanagement practices that can prevent and control feather pecking whilstsimultaneously conferring welfare benefits. The genetic basis of feather peckingis considered, and studies that suggest group selection techniques could producebirds with a reduced tendency to feather peck in commercial flocks arehighlighted.

Keywords

laying henfeather peckingbeak-trimminglightrisk factorgenetic selection

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Type
Review Article
Information
World's Poultry Science Journal , Volume 69 , Issue 4 , December 2013 , pp. 775 - 788
Copyright
Copyright © World's Poultry Science Association 2013 

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References

ABRAHAMSSON, P., FOSSUM, O. and TAUSON, R. (1998) Health of laying hens in an aviary system over five batches of birds. Acta Veterinaria Scandinavica 39: 367-379.CrossRefGoogle Scholar
AERNI, V., EL-LETHEY, H. and WECHSLER, B. (2000) Effect of foraging material and food form on feather pecking in laying hens. British Poultry Science 41: 16-21.CrossRefGoogle ScholarPubMed
BESTMAN, M.W.P. and WAGENAAR, J.P. (2003) Farm level factors associated with feather pecking in organic laying hens. Livestock Production Science 80: 133-140.CrossRefGoogle Scholar
BESTMAN, M., KOENE, P. and WAGENAAR, J.-P. (2009) Influence of farm factors on the occurrence of feather pecking in organic reared hens and their predictability for feather pecking in the laying period. Applied Animal Behaviour Science 121: 120-125.CrossRefGoogle Scholar
BILCIK, B. and KEELING, L.J. (1999) Changes in feather condition in relation to feather pecking and aggressive behaviour in laying hens. British Poultry Science 40: 444-451.CrossRefGoogle ScholarPubMed
BLOKHUIS, H.J., CEPERO, R., COLIN, P., ELSON, A., FIKS VAN NIEKERK, T., KEELING, L., MICHEL, V., NICOL, C.J., OESTER, H. and TAUSON, R. (2005) Welfare aspects of various systems of keeping laying hens. EFSA Journal 197: 1-23.Google Scholar
BLOKHUIS, H.J., FIKS-VAN NIEKERK, T., BESSEI, W., ELSON, A., GUEMENE, D., KJAER, J.B., LEVRINO, G.A.M., NICOL, C.J., TAUSON, R., WEEKS, C.A. and DE WEERD, H.A.V. (2007) The LayWel project: welfare implications of changes in production systems for laying hens. World's Poultry Science Journal 63: 101-114.CrossRefGoogle Scholar
BOLHUIS, J.E., ELLEN, E.D., VAN REENEN, C.G., DE GROOT, J., TEN NAPEL, J., KOOPMANSCHAP, R., DE VRIES REILINGH, G., UITDEHAAG, K.A., KEMP, B. and RODENBURG, T.B. (2009) Effects of genetic group selection against mortality on behaviour and peripheral serotonin in domestic laying hens with trimmed and intact beaks. Physiology & Behavior 97: 470-475.CrossRefGoogle ScholarPubMed
BRIGHT, A., JONES, T.A. and DAWKINS, M.S. (2006) A non-intrusive method of assessing plumage condition in commercial flocks of laying hens. Animal Welfare 15: 113-118.CrossRefGoogle Scholar
BRIGHT, A. (2007) Plumage colour and feather pecking in laying hens, a chicken perspective? British Poultry Science 48: 253-263.CrossRefGoogle Scholar
BRIGHT, A. (2009) Time course of plumage damage in commercial layers. Veterinary Record 164: 334-335.CrossRefGoogle ScholarPubMed
BRIGHT, A., BRASS, D., CLACHAN, J., DRAKE, K.A. and JORET, A.D. (2011) Canopy cover is correlated with reduced injurious feather pecking in commercial flocks of free range laying hens. Animal Welfare 20: 329-338.CrossRefGoogle Scholar
CHOW, A. and HOGAN, J.A. (2005) The development of feather pecking in Burmese red junglefowl: the influence of early experience with exploratory-rich environments. Applied Animal Behaviour Science 93: 283-294.CrossRefGoogle Scholar
DENNIS, R.L., FAHEY, A.G. and CHENG, H.W. (2009) Infrared beak treatment method compared with conventional hot-blade trimming in laying hens. Poultry Science 88: 38-43.CrossRefGoogle ScholarPubMed
DRAKE, K.A., DONNELLY, C.A. and DAWKINS, M.S. (2010) Influence of rearing and lay risk factors on propensity for feather damage in laying hens. British Poultry Science 51: 725-733.CrossRefGoogle ScholarPubMed
ELLEN, E.D., MUIR, W.M. and BIJMA, P. (2007) Genetic improvement of traits affected by interactions among individuals: sib selection schemes. Genetics 176: 489-499.CrossRefGoogle ScholarPubMed
FARM ANIMAL WELFARE COUNCIL (FAWC) (2007) Opinion On beak trimming of laying hens, pages: 12. FAWC, London, UK.Google Scholar
FIKS-VAN NIEKERK, T.G.C.M. and ELSON, H.A. (2004) Abrasive devices to blunt the beak tip, in: GLATZ, P. (Ed.) Poultry Welfare Issues, Volume Beak Trimming, pp. 127-131 (Nottingham University Press).Google Scholar
FOSSUM, O., JANSSON, D.S., ETTERLIN, P.E. and VAGSHOLM, I. (2009) Causes of mortality in laying hens in different housing systems in 2001 to 2004. Acta Veterinaria Scandinavica 51: article 3.CrossRefGoogle ScholarPubMed
FREIRE, R., GLATZ, P.C. and HINCH, G. (2008) Self-administration of an analgesic does not alleviate pain in beak trimmed chickens. Asian-Australasian Journal of Animal Sciences 21: 443-448.CrossRefGoogle Scholar
FREIRE, R., EASTWOOD, M.A. and JOYCE, M. (2011) Minor beak trimming in chickens leads to loss of mechanoreception and magnetoreception. Journal of Animal Science 89: 1201-1206.CrossRefGoogle ScholarPubMed
GENTLE, M.J. and MCKEEGAN, D.E.F. (2007) Evaluation of the effects of infrared beak trimming in broiler breeder chicks. Veterinary Record 160: 145-148.CrossRefGoogle ScholarPubMed
GILANI, A-M., NICOL, C.J. and KNOWLES, T.G. (2011) The effect of range access during rear on feather pecking at lay. Proceedings of the 30th Poultry Science Symposium - Alternative systems for Poultry: health welfare and productivity, Glasgow, pp. 63.Google Scholar
GILANI, A-M. (2012) Investigation of rearing environment and its association with feather pecking in free-range pullets. PhD Thesis, University of Bristol.Google Scholar
GILANI, A-M., NICOL, C.J. and KNOWLES, T.G. (2012) The effect of dark brooders on feather pecking on commercial farms. Applied Animal Behaviour Science 142: 42-50.CrossRefGoogle Scholar
GREEN, L.E., LEWIS, K., KIMPTON, A. and NICOL, C.J. (2000) Cross-sectional study of the prevalence of feather pecking in laying hens in alternative housing systems and its associations with management and disease. Veterinary Record 147: 233-238.CrossRefGoogle ScholarPubMed
GUNNARSSON, S., KEELING, L.J. and and SVEDBURG, J. (1999) Effect of rearing factors on the prevalence of floor eggs, cloacal cannibalism and feather pecking in commercial flocks of loose housed laying hens. British Poultry Science 40: 12-18.CrossRefGoogle ScholarPubMed
HÄNE, M., HUBER-EICHER, B. and FROHLICH, E. (2000) Survey of laying hen husbandry in Switzerland. World's Poultry Science Journal 56: 21-31.CrossRefGoogle Scholar
HUBER-EICHER, B. (1999) A survey of layer-type pullet rearing in Switzerland. World's Poultry Science Journal 55: 83-91.CrossRefGoogle Scholar
HUBER-EICHER, B. and AUDIGE, L. (1999) Analysis of risk factors for the occurrence of feather pecking in laying hen growers. British Poultry Science 40: 599-604.CrossRefGoogle ScholarPubMed
HUBER-EICHER, B. and SEBO, F. (2001) The prevalence of feather pecking and development in commercial flocks of laying hens. Applied Animal Behaviour Science 74: 223-231.CrossRefGoogle Scholar
JENSEN, A.B., PALME, R. and FORKMAN, B. (2006) Effect of brooders on feather pecking and cannibalism in domestic fowl (Gallus gallus domesticus) Applied Animal Behaviour Science 99: 287-300.CrossRefGoogle Scholar
JOHNSEN, P.F., VESTERGAARD, K.S. and NORGAARD-NIELSEN, G. (1998) Influence of early rearing conditions on the development of feather pecking and cannibalism in domestic fowl. Applied Animal Behaviour Science 60: 25-41.CrossRefGoogle Scholar
JONGMAN, E.C., GLATZ, P.C. and BARNETT, J.L. (2008) Changes in behaviour of laying hens following beak trimming at hatch and re-trimming at 14 weeks. Asian-Australasian Journal of Animal Sciences 21: 291-298.CrossRefGoogle Scholar
KEELING, L. and JENSEN, P. (1995) Do feather pecking and cannibalistic hens have different personalities? Applied Animal Behaviour Science 44: 265.CrossRefGoogle Scholar
KEELING, L., ANDERSSON, L., SCHUTS, K.E., KERJE, S., FREDRIKSSON, R., CARLBORG, O., CORNWALLIS, C.K., PIZZARI, T. and JENSEN, P. (2004) Chicken genomics: Feather-pecking and victim pigmentation. Nature 7009: 645-646.CrossRefGoogle Scholar
KJAER, J.B. (2000) Diurnal rhythm of feather pecking behaviour and condition of integument in four strains of loose housed laying hens. Applied Animal Behaviour Science 65: 331-347.CrossRefGoogle Scholar
KJAER, J.B. and JORGENSEN, H. (2011) Heart rate variability in domestic chicken lines genetically selected on feather pecking behavior. Genes, Brain and Behavior 10: 747-755.CrossRefGoogle ScholarPubMed
KJAER, J.B. and SORENSEN, P. (1997) Feather pecking behaviour in White Leghorns, a genetic study. British Poultry Science 38: 333-341.CrossRefGoogle ScholarPubMed
KJAER, J.B. and VESTERGAARD, K.S. (1999) Development of feather pecking in relation to light intensity. Applied Animal Behaviour Science 62: 243-254.CrossRefGoogle Scholar
KNIERIM, U., STAACK, M., GRUBER, B., KEPPLER, C., ZALUDIK, K. and NIEBUHR, K. (2008) Risk factors for feather pecking in organic laying hens - starting points for prevention in the housing environment. 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008. Archived at http;//orgprints.org/view/projects/conference.html.Google Scholar
LAMBTON, S.L., KNOWLES, T.G., YORKE, C. and NICOL, C.J. (2010) The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens. Applied Animal Behaviour Science 123: 32-42.CrossRefGoogle Scholar
LAMBTON, S., NICOL, C.J., FRIEL, M., MAIN, D.C.J., MCKINSTRY, J.L., SHERWIN, C.M., WALTON, J. and WEEKS, C.A. (2013) A bespoke management package can reduce the levels of injurious pecking in loose housed laying hen flocks. Veterinary Record 172: 423-430.CrossRefGoogle ScholarPubMed
LIND, O. and KELBER, A. (2009) Avian colour vision: Effects of variation in receptor sensitivity and noise data on model predictions as compared to behavioural results. Vision Research 49: 1939-1947.CrossRefGoogle ScholarPubMed
MADDOCKS, S.A., CUTHILL, I.C., GOLDSMITH, A.R. and SHERWIN, C.M. (2001) Behavioural and physiological effects of absence of ultraviolet wavelengths for domestic chicks. Animal Behaviour 62: 1013-1019.CrossRefGoogle Scholar
MARCHANT-FORDE, R.M., FAHEY, A.G. and CHENG, H.W. (2008) Comparative effects of infrared and one-third hot-blade trimming on beak topography, behavior, and growth. Poultry Science 87: 1474-1483.CrossRefGoogle ScholarPubMed
MCADIE, T.M. and KEELING, L.J. (2000) Effect of manipulating feathers of laying hens on the incidence of feather pecking and cannibalism. Applied Animal Behaviour Science 68: 215-229.CrossRefGoogle ScholarPubMed
MOHAMMED, H.H., GRASHORN, M.A. and BESSEI, W. (2010) The effects of lighting conditions on the behaviour of laying hens. Archiv für Geflügelkunde 74: 197-202.Google Scholar
MUIR, W.M. (1996) Group selection for adaptation to multiple-hen cages: selection program and direct responses. Poultry Science 75: 447-458.CrossRefGoogle ScholarPubMed
NICKLA, D.L., WILDSOET, C.F. and TROILO, D. (2001) Endogenous rhythms in axial length and choroidal thickness in chicks: Implications for ocular growth regulation. Investigative Ophthalmology & Visual Science 42: 584-588.Google ScholarPubMed
NICOL, C.J., GREGORY, N.G., KNOWLES, T.G., PARKMAN, I.D. and WILKINS, L.J. (1999) Differential effects of increased stocking density, mediated by increased flock size, on feather pecking and aggression in laying hens. Applied Animal Behaviour Science 65: 137-152.CrossRefGoogle Scholar
NICOL, C.J., POETZSCH, C., LEWIS, K. and GREEN, L.E. (2003) A matched concurrent case control study of risk factors for feather pecking in hens on free-range commercial farms in the UK. British Poultry Science 44: 515-523.CrossRefGoogle ScholarPubMed
NICOL, C.J., BROWN, S.N., GLEN, E., POPE, S.J., SHORT, F.J., WARRISS, P.D., ZIMMERMAN, P.H. and WILKINS, L.J. (2006) Effects of stocking density, flock size, and management on the welfare of laying hens in single tier aviaries. British Poultry Science 47:135-146.CrossRefGoogle ScholarPubMed
ODEN, K., KEELING, L.J. and ALGERS, B. (2002) Behaviour of laying hens in two types of aviary systems on 25 commercial farms in Sweden. British Poultry Science 43: 169-181.CrossRefGoogle ScholarPubMed
PÖTZSCH, C.J., LEWIS, K., NICOL, C.J. and GREEN, L.E. (2001) A cross-sectional study of the prevalence of vent pecking in laying hens in alternative systems and its associations with feather pecking, management and disease. Applied Animal Behaviour Science 74: 259-272.CrossRefGoogle Scholar
PRESCOTT, N.B., WATHES, C.M. and JARVIS, J.R. (2003) Light, vision and the welfare of poultry. Animal Welfare 12: 269-288.CrossRefGoogle Scholar
RIBER, A.B. and FORKMAN, B. (2007) A note on the behaviour of the chicken that receives feather pecks. Applied Animal Behaviour Science 108: 337-341.CrossRefGoogle Scholar
RIBER, A.B., NIELSEN, B.L., RITZ, C. and FORKMAN, B. (2007) Diurnal activity cycles and synchrony in layer hen chicks (Gallus gallus domesticus). Applied Animal Behaviour Science 108: 276-287.CrossRefGoogle Scholar
RIEDSTRA, B. and GROOTHUIS, T.G.G. (2002) Early feather pecking as a form of social exploration: the effect of group stability on feather pecking and tonic immobility in domestic chicks. Applied Animal Behaviour Science 77: 127-138.CrossRefGoogle Scholar
RODENBURG, T.B., BIJMA, P., ELLEN, E.D., BERGSMA, R., DE VRIES, S., BOLHUIS, J.E., KEMP, B. and VAN ARENDONK, J.A.M. (2010) Breeding amiable animals? Improving farm animal welfare by including social effects in breeding programmes. Animal Welfare 19: S77-82.CrossRefGoogle Scholar
RODENBURG, T.B., BOLHUIS, J.E., KOOPMANSCHAP, R.E., ELLEN, E.D. and DECUYPERE, E. (2009a) Maternal care and selection for low mortality affect post-stress corticosterone and peripheral serotonin in laying hens. Physiology & Behavior 98: 519-523.CrossRefGoogle ScholarPubMed
RODENBURG, T.B., DE REU, K. and TUYTTENS, F.A.M. (2012) Performance, welfare, health and hygiene of laying hens in non-cage systems in comparison with cage systems, in: SANDILANDS, V. & HOCKING, P. (Eds) Alternative Systems for Poultry – Health, Welfare and Productivity, pp. 210-224 (Glasgow, United Kingdom).Google Scholar
RODENBURG, T.B., TUYTTENS, F.A.M., DE REU, K., HERMAN, L., ZOONS, J. and SONCK, B. (2008) Welfare assessment of laying hens in furnished cages and non-cage systems: an on-farm comparison. Animal Welfare 17: 363-373.CrossRefGoogle Scholar
RODENBURG, T.B., UITDEHAAG, K.A., ELLEN, E.D. and KOMEN, J. (2009b) The effects of selection on low mortality and brooding by a mother hen on open-field response, feather pecking and cannibalism in laying hens. Animal Welfare 18: 427-432.CrossRefGoogle Scholar
RODENBURG, T.B., VAN HIERDEN, Y.M., BUITENHUIS, A.J., RIEDSTRA, B., KOENE, P., KORTE, S.M., VAN DER POEL, J.J., GROOTHUIS, T.G.G. and BLOKHUIS, H.J. (2004) Feather pecking in laying hens: new insights and directions for research? Applied Animal Behaviour Science 86: 291-298.CrossRefGoogle Scholar
RODENBURG, T.B., VAN KRIMPEN, M.M., DE JONG, I.C., DE HAAS, E.N., KOPS, M.S., RIEDSTRA, B.J., NORDQUIST, R.E., WAGENAAR, J.P., BESTMAN, M. and NICOL, C.J. (2013) The prevention and control of feather pecking in laying hens: identifying the underlying principles. World's Poultry Science Journal 69: 361-374.CrossRefGoogle Scholar
SAVORY, C.J. and MANN, J.S. (1999) Feather pecking in groups of growing bantams in relation to floor litter substrate and plumage colour. British Poultry Science 40: 565-572.CrossRefGoogle ScholarPubMed
SEDLACKOVA, M., BILCIK, B. and KOSTAL, L. (2004) Feather pecking in laying hens: Environmental and endogenous factors. Acta Veterinaria Brno 73: 521-531.CrossRefGoogle Scholar
SHERWIN, C.M., RICHARDS, G.J. and NICOL, C.J. (2010) Comparison of the welfare of layer hens in 4 housing systems in the UK. British Poultry Science 51: 488-499.CrossRefGoogle ScholarPubMed
STAACK, M., GRUBER, B., KEPPLER, C., ZALUDIK, K., NIEBUHR, K. and KNIERIM, U. (2007) Importance of the rearing period for laying hens in alternative systems. Deutsche Tierarztliche Wochenschrift 114: 86-90.Google ScholarPubMed
TABLANTE, N.L., VAILLANCOURT, J.P., MARTIN, S.W., SHOUKRI, M. and ESTEVEZ, I. (2000) Spatial distribution of cannibalism mortalities in commercial laying hens. Poultry Science 79: 705-708.CrossRefGoogle ScholarPubMed
TAUSON, R. (2005) Management and housing systems for layers - effects on welfare and production. World's Poultry Science Journal 61: 477-490.CrossRefGoogle Scholar
TAYLOR, P.E., SCOTT, G.B. and ROSE, P. (2003) The ability of domestic hens to jump between horizontal perches: effects of light intensity and perch colour. Applied Animal Behaviour Science 83: 99-108.CrossRefGoogle Scholar
UITDEHAAG, K., KOMEN, H., RODENBURG, T.B., KEMP, B. and VAN ARENDONK, J. (2008) The novel object test as predictor of feather damage in cage-housed Rhode Island Red and White Leghorn laying hens. Applied Animal Behaviour Science 109: 292-305.CrossRefGoogle Scholar
UITDEHAAG, K.A., RODENBURG, T.B., BOLHUIS, J.E., DECUYPERE, E. and KOMEN, H. (2009) Mixed housing of different genetic lines of laying hens negatively affects feather pecking and fear related behaviour. Applied Animal Behaviour Science 116: 58-66.CrossRefGoogle Scholar
VAN DE WEERD, H.A. and ELSON, A. (2006) Rearing factors that influence the propensity for injurious feather pecking in laying hens. World's Poultry Science Journal 62: 654-664.Google Scholar
VAN HIERDEN, Y.M., KORTE, S.M., RUESINK, E.W., VAN REENEN, C.G., ENGEL, B., KOOLHAAS, J.M. and BLOKHUIS, H.J. (2002) The development of feather pecking behaviour and targeting of pecking in chicks from a high and low feather pecking line of laying hens. Applied Animal Behaviour Science 77: 183-196.CrossRefGoogle Scholar
VAN HORNE, P.L.M. and ACHTERBOSCH, T.J. (2008) Animal welfare in poultry production systems: impact of EU standards on world trade. World's Poultry Science Journal 64: 40-51.CrossRefGoogle Scholar
WEITZENBÜRGER, D., VITS, A., HAMANN, H. and DISTL, O. (2005) Effect of furnished small group housing systems and furnished cages on mortality and causes of death in two layer strains. British Poultry Science 46: 553-559.CrossRefGoogle ScholarPubMed
YNGVESSON, J., GUSTAFSON, J., BERG, C., LARSSON, I., GUNNARSSON, S. and ODEN, K. (2011) A field study of access to day light, ammonia, plumage condition and mortality in loose housed laying hens in south east Sweden. Proceedings of the 30th Poultry Science Symposium - Alternative systems for Poultry: health welfare and productivity, Glasgow, pp. 53.Google Scholar
ZELTNER, E. and HIRT, H. (2003) Effect of artificial structuring on the use of laying hen runs in a free-range system. British Poultry Science 44: 533-537.CrossRefGoogle Scholar
ZIMMERMAN, P.H., LINDBERG, A.C., POPE, S.J., GLEN, E., BOLHUIS, J.E. and NICOL, C.J. (2006) The effect of stocking density, flock size and modified management on laying hen behaviour and welfare in a non-cage system. Applied Animal Behaviour Science 101: 111-124.CrossRefGoogle Scholar