Breed-related differences in the preference for inanimate objects between chicks of laying hens

Abstract

Our previous study showed significant behavioural differences between breeds of laying hens. Birds differed in their excitability, reactivity, decision-making speed, behavioural strategy, and interest in elements of the surroundings. The results of our investigations and studies conducted by other authors raised a question of potential differences between chicks of different breeds in their preference for objects mimicking a member of their social group or a potential predator. Theoretically, the answer to the question was provided tens of years ago; however, new insight into this problem was provided by some researchers in experiments where breed-related differences associated with imprinting were demonstrated. Therefore, we have now asked questions whether reactions to objects imitating chick's mother and a predator may differ between breeds and whether the history of selection of the breed may be associated with chicks' preference for specific objects. We have also tried to verify whether the fact that the chicks have not been in contact with such objects for many generations has an impact on their ability to discriminate between the objects.The study involved three breeds (Green-legged partridge - Zk, Leghorn - Lg, and Crested hen - Ch) differing in their selection history, laying performance, and purpose of breeding. Lg hens are particularly suitable for intensive farming, Zk is a primitive breed used in extensive farming, and Ch is a general-purpose breed intended for organic farming. The preference of 1- and 5-day-old chicks for an object imitating the mother (a stuffed hen) and a potential predator (a stuffed polecat) was examined. Chicks' activity and preference were assessed. The registered traits were subjected to one-way analysis taking into account Bernoulli distribution using the linear model of the GLIMMIX procedure of SAS software (Statistical Analysis System, 9.4, 2013). Orthogonal contrasts were used to verify comparisons of genetic group effects using the Holm-Bonferroni correction.A surprising finding was the preference of the Lg chicks for the stuffed polecat. The Zk and Ch chicks clearly preferred the hen. The differences in the preference for the object between the breeds were significant, whereas no differences were found between the chicks' activity. Each breed was dominated by active chicks making a specific choice. It seems that the intensive selection towards high laying performance may lead to social predisposition anomalies through a correlated reaction, and the Lg breed can be a research model for this type of disorders.