Genetics of the Novel Object Test outcome in laying hens

The purpose of the study was to answer the question whether the behavioural reactions to a novel object can serve as a criterion in selection toward lowering the fearfulness level in laying hens. Fear can be a harmful emotional state resulting from perceiving of an experience as a potential danger. High level of fearfulness is negatively correlated with the overall laying performance. Reactions to the Novel Object Test (NOT) of 9483 Rhode Island White (RIW) and 4326 Rhode Island Red (RIR) hens were camera recorded for 30 s per hen. Six reactions were defined following the analysis of the footage: escape, observing, avoidance, approach, avoidance-approach, and pecking. A hen was attributed only one reaction, and no other combinations were encountered. The variance components of the reactions regarded the animal additive genetic and the residual effects and were estimated with Gibbs sampling software accounting for binomial character of the NOT output. Two groups of reactions positively correlated within a group and negatively between the groups allowed for distinguishing of two behavioural profiles − “exploratory” (observing, approach, pecking) and “fearful” (avoidance-approach, avoidance, escape). The rearranged into profiles output of NOT (two-trait) was processed with the same model to estimate the genetic parameters for the profiles. The genetic correlations between the profiles were negative at ca. 0.70 while the heritabilities reached 0.17/0.19 for the exploratory profile and 0.19/0.08 for the fearful profile, in RIW/RIR. Except for the heritability of the fearful profile in RIR, the profile heritabilities were higher than heritability of any of the 6 basic reactions. Our recommendation is to indirectly lower the fearfulness level by selecting for exploratory behaviour based either on the exploratory profile or on the basic behaviour of pecking alone as this is a reaction of a sufficiently high heritability (0.13-0.16) and easy to define.