Litter substrates as enrichment components

In enriched cage systems some substrate should be provided to allow foraging behaviour and potentially dustbathing behaviour, but full expression of these behaviours is not possible. It has been shown that dustbathing behaviour in enriched cages is often disturbed and vacuum dustbathing on wire is common, indicating that the supplied litter is inappropriate.

Alternative systems provide more opportunities to perform dustbathing and foraging but also here full expression of these behaviours is not observed. Thus, with respect to laying hen welfare it is important to know what resources are most appropriate for full expression of dustbathing and foraging behaviour. Moreover, it would be useful to know if there should be a requirement to provide additional resources over and above the pecking and scratching area in enriched cages, e.g. a dustbathing area.

As reported in deliverable 4.3, substrate preference of laying hens with respect to dustbathing and foraging behaviour were investigated in order to determine which resources should be provided in laying hen housing systems for the expression of these behaviours. The consumer demand approach was used to study the strength of preference. Hens had to push a weighted door to enter choice pens with a wire floor, sand, wood shavings or peat moss as substrate. Twelve Isa-Brown hens, reared on battery cages, successfully learned to open the push door . Most of the hens worked for getting access to all choice pens. The slopes of the demand curves for the number of entries to the choice pens were steep and not significantly different (Figure 1). Also no differences were found in the maximum price paid and the total expenditure. These data indicate that there seems to be no preference for wire or any substrate per se. However, with respect to dustbathing, almost all hens worked for getting access to peat moss to take a dustbath whereas only some hens worked for sand or wood shavings. The slope of the demand curve for dustbathing in peat moss was relatively shallow and the maximum price paid and the total expenditure to take a dustbath in peat moss were significantly higher as compared to dustbathing in sand or wood shavings. With respect to foraging no clear substrate preference was found. It could be concluded that the value of a particular substrate varies with the behaviour performed in the substrate and that there is a strong demand for peat moss for dustbathing.

Figure 1 The effect of door weight on the percentage of time in the unweighted home pen
and each choice pen. Different letters indicate significant differences per weight
category (P<0.05 at least) (n=12 hens). From Delivarable 4.3.