7th World Congress on Genetics Applied to Livestock Production, August 19-23, 2002, Montpellier, France FEATHER PECKING BEHAVIOUR AND STRESS RESPONSE IN LAYING HENS : A QTL-ANALYSIS A.J. Buitenhuis 1 , T.B. Rodenburg 2 , Y.M. van Hierden 4 , B. Ask 1 , M. Siwek 1 , S.J.B. Cornelissen 1 , M.G.B. Nieuwland 3 , H. Vos 1 , P. de Groot 1 , S.M. Korte 4 , P. Koene 2 , H. Bovenhuis 1 and J. J. van der Poel 1 1 Animal Breeding and Genetics Group 2 Ethology Group 3 Adaptation Physiology Group, Wageningen Institute of Animal Sciences, Wageningen University, P.O. Box 338, NL-6700 AH Wageningen, The Netherlands 4 Department of Behaviour, Stress Physiology and Management, Institute for Animal Science and Health (ID-Lelystad BV), P.O. Box 65, NL- 8200 AB Lelystad, The Netherlands INTRODUCTION The concern for animal welfare in the west European countries results in a change in housing systems. In poultry, the free-range housing systems allow the birds to walk around freely. However, one major drawback is that feather pecking (FP) behaviour occurs. This behaviour can cause feather damage to the birds and ultimately the birds can be pecked to death. The increased feed intake due to the loss of feathers results in economic losses. To prevent the damage of FP, beak-trimming is a common used method (Gentle, 1986) as well as using a dimmed light scheme (Blokhuis and Wiepkema, 1998). However, in some countries beak- trimming is prohibited or will be prohibited in the near future. Therefore, it is important to identify the underlying factors for this behaviour. Although environmental factors play an important role in FP behaviour, differences in FP behaviour between strains suggest a genetic basis. The heritability estimates for FP range from 0.04 (no S.E. mentioned) to 0.56±0.25, depending on age and method of recording (e.g. scoring of plumage condition, direct observations) (Cuthbertson, 1980 ; Bessei, 1995 ; Kjaer and Sørensen, 1997 ; Kjaer et al., 2001 ; Rodenburg et al., 2002). The possibility to select for FP behaviour seems feasible, as using the number of performed bouts as a selection criterion for FP has been succesful (Kjaer et al., 2001). Craig and Muir (1993) have succesfully reduced mortality due to beak inflicted injuries based on group selection. Selection lines are useful to identify underlying genetic, immunological and physiological factors for FP behaviour. Differences in immune-response, serotonin levels and stress hormones as a consequence of selection for a reduced mortality have been reported (Cheng et al., 2001a,b). Korte et al., 1997 reported a difference in physiology (corticosterone level) between a high FP and a low FP line. More recently, van Hierden et al., (2002) found that the dopamine and serotonin turnover was lower in a high FP strain than in a low FP strain. Suggesting that differences in the development and performance of FP between the two lines are associated with a difference in physiology and neurobiology. The use of molecular genetics can be of great value to identify the chromosomal regions and genes involved in behaviour and stress response. The aim of this paper is to describe a QTL mapping experiment to identify chromosomal regions involved in behaviour traits in laying hens and to estimate the h 2 of the corticosterone response after manual restraint. Session 14. Behaviour and welfare Communication N° 14-06