Date Published: May 2, 2019
Publisher: Public Library of Science
Author(s): Changsheng Nie, Liping Ban, Zhonghua Ning, Lujiang Qu, Arda Yildirim.
Aggression in chickens is a serious economic and animal welfare issue in poultry farming. Pigmentation traits have been documented to be associated with animal behaviour. Chicken pecking behaviour has been found to be related to feather colour, with premelanosome protein 17 (PMEL17) being one of the candidate genes. In the present study, we performed a genotypic and phenotypic association analysis between chicken plumage colour (red and white) and aggressive behaviour in an F1 hybrid group generated by crossing the autosomal dominant white-feathered breed White Leghorn (WL) and the red-feathered breed Rhode Island Red (RIR). In genetic theory, all the progeny should have white feathers because WL is homozygous autosomal dominant for white feathers. However, we found a few red-feathered female chickens. We compared the aggressiveness between the red and white females to determine whether the feather colour alone affected the behaviour, given that the genetic background should be the same except for feather colour. The aggressiveness was recorded 5 days after sexual maturity at 26 weeks. Generally, white plumage hens showed significantly higher aggressiveness compared to the red ones in chasing, attacking, pecking, and threatening behaviour traits. We assessed three candidate feather colour genes—PMEL17, solute carrier family 45 member 2 (SLC45A2), and SRY-box 10 (SOX10)—to determine the genetic basis for the red and white feather colour in our hybrid population; there was no association between the three loci and feather colour. The distinct behavioural findings observed herein provide clues to the mechanisms underlying the association between phenotype and behaviour in chickens. We suggest that mixing red and white chickens together might reduce the occurrence of aggressive behaviours.
Aggressive behaviour in chickens is a widespread economic and animal welfare issue in poultry farming, and many factors such as food, mates, and social rank affect its occurrence [1, 2]. Such behaviour has different forms (threats and intense agonistic behaviour) and is divided into numerous types such as still threats, chasing, aggressive pecking, and attacks . As a complex trait in chicken, aggressiveness has been found to be present, albeit with low heritability (h2 = 0.04–0.17) in various studies [4–8], and aggressive pecking has been reported to be affected by a variety of environmental factors, including light intensity , stocking density [10, 11], food , feeding methods , group size , and male presence . Moreover, appearance factors such as comb type , plumage pattern , and plumage colour  can also influence the behaviour of chickens. Therefore, aggressive behaviour in chickens is a function of interaction among genes, phenotype, and environment.
All procedures and protocols (DOI: dx.doi.org/10.17504/protocols.io.ysgfwbw) involving animals were conducted in accordance with the Guidelines for the Care and Use of Experimental Animals established by the Ministry of Agriculture of China (Beijing, China). All the animal protocols were approved by the Animal Welfare Committee of China Agricultural University (Beijing, China, Permit Number: XK622).
The domestication of animals is associated with feather or coat colour changes in various animal species [22, 30]. In mammals, these observations suggest that domestication has a co-evolutionary effect of inducing pigment loss and tame behaviour, which has also been proven in birds.
In the present F1 cross population, white-feathered hens were more aggressive than the red ones were. Compared with raising white chickens together, mixing red and white chickens together can reduce the occurrence of aggressive behaviours. Moreover, these differences in behaviour and phenotype were not caused by PMEL17, SOX10, or SLC45A2, which provide a good model for behavioural research of individual birds with different feather colours. Taken together, the distinct behavioural findings observed in this study provide novel insights into the mechanisms underlying the association between phenotype and behaviour in the present population and other chicken breeds.