Genetic correlations between behavioural responses and performance traits in laying hens

Abstract

ObjectiveThe aim of the study was to evaluate genetic correlations between the behavioural profile and performance in laying hens as an indirect answer to the question whether the observed behavioural responses are associated with increased levels of stress in these birds.MethodsThe assessment of birds’ temperament was carried out using the novel objects test. The behavioural test was conducted in two successive generations comprising 9,483 Rhode Island White (RIW) birds (approx. 4,700 individuals per generation) and 4,326 Rhode Island Red (RIR) birds (approx. 2,100 individuals per generation). Based on the recorded responses, the birds were divided into two groups: a fearful profile (1,418 RIW hens and 580 RIR hens) and a brave/curious profile (8,065 RIW hens and 3,746 RIR hens). The birds were subjected to standard assessment of their performance traits, including SM, age at sexual maturity; ST, shell thickness; SG, egg specific gravity; EW, mean egg weight; IP, initial egg production; and HC, number of hatched chicks. The pedigree was three generations deep (including two behaviour-recorded generations). Estimation of the (co)variance components was performed with the Gibbs sampling method, which accounts for the discrete character of the behavioural profile denotation.ResultsThe analyses revealed negative correlations between the performance traits of the laying hens and the behavioural profile defined as fearful. In the group of fearful RIW birds, delayed sexual maturation (0.22) as well as a decrease in the initial egg production (−0.30), egg weight (−0.54), egg specific gravity (−0.331), shell thickness (−0.11), and the number of hatched chicks (−0.24) could be expected. These correlations were less pronounced in the RIR breed, in which the fearful birds exhibited a decline in hatchability (−0.37), egg specific gravity (−0.11), and the number of hatched chicks (−0.18). There were no correlations in the case of the other traits or they were positive but exhibited a substantial standard error, as for the egg weight.ConclusionTo sum up the results obtained, it can be noted that behavioural responses indicating fearfulness, i.e. escape, avoidance, and approach-avoidance may reflect negative emotions experienced by birds. The negative correlations with performance in the group of fearful hens may indirectly indicate a high level of stress in these birds, especially in the white-feathered birds, where stronger performance-fearfulness correlations were found. Fearful birds should be eliminated from breeding by inclusion of the behavioural profile in the selection criterion in the case of laying hens.

Behavioural Variability in Chicks vs. the Pattern of Behaviour in Adult Hens

“…The present study also confirms that fearfulness is one of the temperament traits differentiating the breeds from the first days of life (Table 6). This trait in animals is characterised by a high inheritance rate, which has also been confirmed in laying hens [6,7]. The study has shown that fearfulness changes over time, exhibiting a downward trend in older chicks, which may be associated with habituation to a given stimulus.…”

“…As demonstrated in many studies, the level of additive variability is so high that selection for modification of chicken's temperament may bring positive effects [6,7,12]. Currently, behavioural selection is mainly targeted at reduction of aggression and pterophagy [13,14].…”

“…Since the behavioural patterns depend on the genetic background, previous bird's experiences, environmental conditions prevailing during embryonic development, and epigenetic effects [4,[6][7][8][9], a question was posed whether the differences observed in the behaviour of the three breeds (Zk, Lg, Pb) were innate breed-specific behavioural patterns or whether they were "generated" by their living environment. In other words, the question was whether the rearing practice, which was not adjusted to the genetic predisposition of the breed, was the cause of the behavioural differences or whether the breed-specific differences occurred regardless of the rearing practices.…”

Behaviour and stress in three breeds of laying hens kept in the same environment

“…It may be debated whether the behaviour of Lg hens is associated with the large-scale production of the breed as a result of the reaction correlated between performance and behavioural traits (Rozempolska-Rucińska et al, 2017) or whether the differences are associated with the white colour of feathers. White laying hens have been shown to be reactive and demonstrate an intense hormonal and behavioural response to stress compared with brown hens (Fraisse & Cockrem, 2006;Ulitdehaag et al, 2011;de Haas et al, 2013;Pusch et al, 2018).…”

Analysis of Behavioural Profile of Hens with the Use of Computer Software

“…On the basis of our previous studies (Rozempolska-Rucinska et al, 2017) all hens were classified according to their behaviour, to the one of 6 groups: escape (34 individuals)-birds with sudden movements, attempting to go outside the cage; avoidance (35 individuals)-birds moving away from the object but without sudden movements; avoidance-approach (35 individuals)-birds with alternate reactions: approach and moving away from the object; observation (44 individuals)-birds standing in one position with minor head or torso movements, observing the object and not approaching nor distinctly moving away from the object; approach (23 individuals)-approaching to the object, heading towards the object and observing it; pecking (29 individuals)-approaching to the object with one or multiple pecking on the object. Detailed information on the test performance and classification of laying hens to a specified group was given by Rozempolska et al, 2017aRozempolska et al, , 2017b The next step was the analysis of behavioural reactions with the use of Java-based free software, Tracker 4.95 ® (Brown, 2012) for motion analysis allowing determination of multiple movement parameters. Each video clip was analysed with a frame-by-frame method with step size of 20 frames which refers to an interval of 0.8 second.…”