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Domestication and early experiences in chickens: Behavior, stress and gene expression
Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A number of animal species have undergone domestication, the process of becoming adapted to living in captivity and in proximity to humans. Common for these species is that they have all developed certain traits, including changes to coat color, body size and level of fearfulness. This has been termed the domestic phenotype. Among these traits is also an attenuation of the response to stress, both behaviorally and physiologically. Thus, release of glucocorticoids such as cortisol or corticosterone is lower in domesticated species. However, the underlying mechanism for this is not yet well understood. In this thesis, we have investigated genetic mechanisms for the attenuation of the physiological stress response in ancestral chickens, the Red Junglefowl, and domesticated chickens, the White Leghorn.

We found a number of genes that differed in expression between the two breeds in several tissues involved in the stress response. Among the most interesting findings were lower expression of genes involved in production and secretion of ACTH in the pituitary, and in the production of glucocorticoids in the adrenal glands, in the domesticated White Leghorns. We also found higher expression of the glucocorticoid receptor in White Leghorns, indicating that they may have a more efficient negative feedback of the physiological stress response.

We then investigated the transcriptome of the chicken pituitary more closely, and we discovered that a number of genes highly involved in several important physiological axes showed differential expression between the ancestral and the domesticated breed. Among these were genes involved in the stress response, the reproductive system, and in metabolism and growth. As these traits are modified in domesticated species, our results suggest that changes to gene expression in the pituitary may be an important underlying factor of the domestic phenotype.

A separate aim of this thesis was to investigate effects of hatching time in chickens on their subsequent phenotype. Time of hatching constitutes an early experience that may differ between individuals, and we therefore hypothesized that differences in hatching time would affect chickens later in life. While a number of studies have been performed on hatching time and post-hatch growth, very little work has been done on effects on behavior. We found that the time of hatching had sex-specific effects. Hatching times in females were negatively correlated with body weight, whereas in males, behaviors such as reaction to novelty and spatial learning were affected.

As time of hatching is governed by various hormones, including thyroid hormone and corticosterone, we suggest that changes to the levels of these hormones could affect both hatching time and post-hatch phenotypes. Understanding these mechanisms better would be beneficial in terms of production, where batch homogeneity is important, in research on early experiences and the potential for maternal programming, and in evolutionary questions on trade-off between different life strategies.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. , p. 30
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1795
National Category
Other Biological Topics
Identifiers
URN: urn:nbn:se:liu:diva-143053DOI: 10.3384/lic.diva-143053ISBN: 9789176853924 (print)OAI: oai:DiVA.org:liu-143053DiVA, id: diva2:1158180
Presentation
2017-12-15, Schrödinger, E324, Fysikhuset, Campus Valla, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2017-11-17Bibliographically approved
List of papers
1. Chicken domestication changes expression of stress-related genes in brain, pituitary and adrenals
Open this publication in new window or tab >>Chicken domestication changes expression of stress-related genes in brain, pituitary and adrenals
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2017 (English)In: Neurobiology of stress, ISSN 2352-2895, Vol. 7, p. 113-121Article in journal (Refereed) Published
Abstract [en]

Domesticated species have an attenuated behavioral and physiological stress response compared to their wild counterparts, but the genetic mechanisms underlying this change are not fully understood. We investigated gene expression of a panel of stress response-related genes in five tissues known for their involvement in the stress response: hippocampus, hypothalamus, pituitary, adrenal glands and liver of domesticated White Leghorn chickens and compared it with the wild ancestor of all domesticated breeds, the Red Junglefowl. Gene expression was measured both at baseline and after 45 min of restraint stress. Most of the changes in gene expression related to stress were similar to mammals, with an upregulation of genes such as FKBP5, C-FOS and EGR1 in hippocampus and hypothalamus and StAR, MC2R and TH in adrenal glands. We also found a decrease in the expression of CRHR1 in the pituitary of chickens after stress, which could be involved in negative feedback regulation of the stress response. Furthermore, we observed a downregulation of EGR1 and C-FOS in the pituitary following stress, which could be a potential link between stress and its effects on reproduction and growth in chickens. We also found changes in the expression of important genes between breeds such as GR in the hypothalamus, POMC and PC1 in the pituitary and CYP11A1 and HSD3B2 in the adrenal glands. These results suggest that the domesticated White Leghorn may have a higher capacity for negative feedback of the HPA axis, a lower capacity for synthesis of ACTH in the pituitary and a reduced synthesis rate of corticosterone in the adrenal glands compared to Red Junglefowl. All of these findings could explain the attenuated stress response in the domesticated birds.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Animal domestication, Chicken, Gene expression, Glucocorticoid receptor, HPA axis, Stress response
National Category
Genetics
Identifiers
urn:nbn:se:liu:diva-143054 (URN)10.1016/j.ynstr.2017.08.002 (DOI)28879214 (PubMedID)2-s2.0-85028334770 (Scopus ID)
Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2017-11-30Bibliographically approved
2. Effects of Hatching Time on Behavior and Weight Development of Chickens
Open this publication in new window or tab >>Effects of Hatching Time on Behavior and Weight Development of Chickens
2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 7, p. e103040-Article in journal (Refereed) Published
Abstract [en]

The length of the embryonic period varies both among and within species and can affect the individual phenotype in many ways, both physiologically and behaviorally. In chickens, the hatch window may last 24-48 hours (up to 10% of the incubation time), and studies have shown that incubation length may affect post-hatch growth and physiology. However, little is known about effects on behavior. We therefore investigated how behavior variation correlates with hatching time in the early life of chickens. We also measured egg weight and egg weight loss in relation to hatching time, as well as post-hatch growth. For females, there was a negative correlation between hatch time and body weight from day 4 and throughout the experiment. For males, such a correlation was only observed when testing all hatched males up until day 10. The birds were exposed to a number of behavioral tests, and a principal components analysis was performed on the variables, resulting in four components. For the largest component, termed "Passivity, a tendency of a difference was found between early and middle male hatchers. Furthermore, a significant difference between early and middle male hatchers was found in the second component, termed "Response to novelty. In a spatial learning test, late hatchers tended to learn slower. The behavior of females was not significantly affected by hatching time in any of these tests. This study is among the first to demonstrate a link between time of hatching and early behavior in a precocial species like the chicken, and may help shedding light on the evolutionary trade-offs between incubation length and post-hatch traits. The results may also be relevant from a perspective of stress coping and therefore also for animal welfare and productivity in the chicken industry. The mechanisms linking hatching time with post-hatch phenotype remain to be investigated.

Place, publisher, year, edition, pages
Public Library of Science, 2014
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-111296 (URN)10.1371/journal.pone.0103040 (DOI)000341354800055 ()25058654 (PubMedID)
Note

Funding Agencies|Swedish Research Council; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas); European Research Council

Available from: 2014-10-14 Created: 2014-10-14 Last updated: 2017-12-05

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