Variability of laying hen behaviour depending on the breed

Abstract

Objective For many generations, most species of farm animals have been subjected to intense and strictly targeted selection for improvement of their performance traits. This has led to substantial changes in animal anatomy and physiology, which resulted in considerable differences between the current animal breeds and their wild ancestors. The aim of the study was to determine whether there is breed-specific variability in behaviour as well as differences in emotional reactivity and preferences of laying hens. Methods The investigations involved 50 Green-legged Partridge, 50 Polbar, and 50 Leghorn hens. All birds were kept in the same conditions, and the behavioural tests were carried out at 30 weeks of age. We used the tonic immobility test and a modified open-field test including such objects as water, commercial feed, feed enriched with cereal grains, finely cut straw, and insect larvae, a sandpit, a mirror, and a shelter imitating a hen nest. Results The research results demonstrate that the birds of the analysed breeds differ not only in the excitability and emotional reactivity but, importantly, also in the preferences for environment-enriching elements. Ensuring hens’ well-being should therefore be based on environmental modifications that will facilitate acquisition of essential elements of chickens’ behaviour. The greatest emotional reactivity was found in the Leghorn breed, which may be a result of correlated selection aimed at an increase in chicken productivity. Conclusion The differences in the behaviour of the birds from the analysed breeds indicate that laying hens cannot be regarded as one group of animals with the same environmental requirements.

Level of stress in relation to emotional reactivity of hens

“…The correlation coefficient was only slightly higher than 0.2; yet, it indicates that birds with a higher level of stress may need a longer time before the occurrence of tonic immobility. Concurrently, previous studies showed that tonic immobility was more difficult to achieve by excitable birds with increased emotional reactivity (Kozak et al 2019). This reaction may also be used as an indirect indicator the stress level in hens.…”

“…Birds experiencing negative emotions would not show interest in the surrounding objects (Hocking et al 2001;Rodenburg et al 2003;de Haas et al 2013). The birds' behaviour in MOFT can be linked to negative or positive emotions (Kozak et al 2019), but the level of stress cannot be assessed based on the hens' reactions observed in the test. The behavioural response to a specific stimulus may be analogous in a situation of stress and in a situation when the HPA axis is not activated (Cockrem and Silverin 2002).…”

“…The modified open-field test (OFT) was carried out as in Rodenburg et al (2003) and Kozak et al (2019). To this end, a special observation box with a 1.25 Â 1.25 m floor divided into 25 squares with an area of 25 Â 25 cm each was constructed.…”

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

“…It appears that birds' environmental needs may vary not only between species but also between breeds [3] and individuals of the same breed [4]. Previous investigations [3,5] have demonstrated that hens from three different breeds (green-legged partridge-Zk, Polbar-Pb, and Leghorn-Lg) kept in environments as identical as possible not only differed in the level of activity, emotional arousal, or degree of curiosity, but also preferred different enrichments of the environment, which collectively resulted in a different level of stress in the birds [5]. The Zk breed showed interest in objects that allowed scratching and searching, i.e., the birds preferred a container filled with finely shredded straw and woodchips as well as insect larvae but ignored a feed container, shelter box, or mirror.…”

“…Both breeds had a higher level of stress than the Zk chicks. The authors reported that the living environment fulfilled the needs of the Zk breed only, but failed to satisfy the needs of the Lg hens [3,5]. The birds were kept on bedding and thus the need of the Zk chickens to scratch and search was satisfied.…”