Effect of whole wheat and feed pellets distribution in the litter on broilers' activity and performance.

Broilers have been subjected for decades to intensive genetic selection for growth rate and feed conversion. This resulted in significantly shorter fattening period but also in numerous skeletal and cardiovascular diseases (EMMERSON, 1997). Leg disorders have been recognized as a major cause of poor animal welfare in commercial broiler production (EU, 2000). Twenty-six to 30% of broilers have leg problems (SANOTRA et al., 2003), which are likely painful (PICKUP et al., 1997). Those birds whose walking ability is substantially impaired tend to be lighter (HAYE and SIMONS, 1978; KESTIN et al., 1999) and may suffer from thirst or hunger due to inability of reaching drinkers and feeders (BUTTERWORTH et al., 2002). However, leg disorders do not only present serious welfare problem, but may also cause economical losses. Over 2% of animals die or need to be culled because of leg problems (GRASHORN, 1987). Nevertheless, it has been reported that the onset of leg disorders can be reduced or delayed with increased physical activity (HAYE and SIMONS, 1978; REITER and BESSEI, 1998; REITER, 2004). Mechanical stress on the locomotor system caused by locomotion activates bone formation processes and improves bone quality (DJUKIC STOJCIC and BESSEI, 2009; REITER and BESSEI, 1998). Broilers spend about 60% (BOKKERS and KOENE, 2003; MURPHY and PRESTON, 1988) to 90% (ARNOULD and FAURE, 2003; REITER, 2004; WEEKS et al., 2000) of their time inactive. It was assumed that selection for higher growth rate and for more efficient feed conversion decreased broiler’s spontaneous activity (REITER and KUTRITZ, 2001; WEEKS et al., 2000). Additionally, selection for rapid growth of breast muscle resulted in change of body conformation, that is moving the centre of body gravity forward (CORR et al., 2003a). This unbalances the birds and causes standing and moving to be energy consuming and tiring (CORR et al., 2003b). Furthermore, it seems that walking is painful even for birds with rather good walking ability (MCGEOWN et al., 1999). For these reasons it is very difficult to stimulate physical activity in broilers. Attempts to achieve this with increment of environmental complexity by offering strings, sand trays (ARNOULD et al., 2004; LETERRIER et al., 2001), barriers between drinkers and feeders (BIZERAY et al., 2002a), toys and ramps (BALOG et al., 1997; BESSEI, 1992a), were not very successful. However, locomotor activity was enhanced by offering broilers bales of straw (KELLS et al., 2001), by increasing the distance between feeders and drinkers (REITER and BESSEI, 1996), sequential feeding (BIZERAY et al., 2002c), modification of light programs (SANOTRA et al., 2002; SCHWEAN-LARDNER et al., 2006; SCHWEAN, 2002), and high light intensity (HESTER, 1994; NEWBERRY et al., 1986; OLANREWAJU et al., 2006). One of the possibilities to enhance locomotor activity in chickens is the stimulation of foraging behaviour. Scattering whole grain in the litter has been used traditionally in deep litter systems for laying hens. It is known as useful means to elicit foraging behaviour, and thus, to increase scratching and locomotor activity (APPLEBY et al., 2004). The aim of our study was to apply this procedure in broilers. We tried to achieve this by a) scattering whole wheat grains in the litter in addition to standard feed offered ad libitum in a trough and b) removal of feed trough and scattering standard pellets in the litter.