What affects egg color in your Ameraucana flock?
There are several factors that can affect egg color in your Ameraucana flock!
Biliverdin is the pigment responsible for creating blue eggshells in Ameraucana.
Biliverdin is created within the shell gland and is then deposited on the eggshell roughly 3-4 hours before ovi-position (Wang, et al., 2009). The SLCO1B3 gene is the key gene that regulates blue eggshell color. The SLCO1B3 gene is a part of the organic anion transporting polypeptide (OATP) family. The OATPs function as membrane transporters and transport bile products such as Biliverdin.
One study of blue eggshell layers found that the expression level of the SLCO1B3 gene was significantly higher at 25 and 30 weeks during the laying period, and that the overall methylation rate of the SLCO1B3 gene increased gradually with increasing weeks of egg production. As the level of methylation increased, methylation of the CpG5 and CpG8 sites hindered the binding of transcription factors to the promoter, reducing the expression of SLCO1B3 during the late period which resulted in a lighter blue eggshell color. A study in 2011 also found that there was a decline in blue eggshell color with laying order, indicating pigment limitation for females. These two studies reflect that eggshell color becomes lighter with each additional week in the laying cycle.
In one study blue eggshell color was studied on over 400 eggs at the moment of oviposition, at the onset of incubation, and at the end of incubation using a spectrophotometer. Results showed that egg color faded significantly during the study period. This means that time-related (temporal) changes in egg color occur.
One study found that females who experience a decline in antioxidant capacity due to food limitation experience a reduction in blue eggshell color. Another study found that eggshell color is positively related to the concentration and amount of carotenoids and vitamin E in the yolk. (Hargitai et al., 2013). A study in 2017 found that females who experience a decline in antioxidant capacity due to food limitation experience a reduction in blue‐green eggshell color. These studies reflect that a hen’s diet and access to nutrients affect eggshell color.
A study in 2012 identified that the blue color of eggshells can reflect a female’s physiological condition, with only high‐quality females having adequate antioxidant capacity to pigment their eggs with large amounts of biliverdin. This eludes to the impact of a hen’s health on eggshell color.
A study in 2014 showed that eggshell pigmentation is not only affected by female body condition but is also shaped by the female’s early life experience including exposure to stress. In this study eggshell color was influenced by breeding conditions which stresses the relationship between eggshell pigment concentrations and environmental conditions.
Several studies have shown that in hens who lay eggs that have an olive green or khaki spectrum, a coating of the pigment protoporphyrin-IX has been added to the egg during the final hours of the egg being inside the uterus. The higher the concentration of biliverdin within the uterus of a hen, the bluer the egg will be. The higher the concentration of protoporphyrin-IX within the uterus of a hen, the more olive or brown an egg will be (Wang et al., 2009). This eludes to the impact of protoporphyrin-IX on eggshell color.
In closing, the following factors can affect eggshell color in your Ameraucana flock:
✔️Biliverdin
✔️Laying Cycle
✔️Time-Related (Temporal) Changes
✔️Diet and Access to Nutrients
✔️Health
✔️Environmental Conditions
✔️Protoporphyrin-IX
Dearborn, D. Daniel Hanley, Katherine Ballantine, John Cullum, DeeAnn M. Reeder. Eggshell color is more strongly affected by maternal identity than by dietary antioxidants in a captive poultry system. Functional Ecology Volume 26, Issue 4 p. 912-920 Animal physiological ecology. First published: 18 May 2012
https://doi.org/10.1111/j.1365-2435.2012.02001.xHargitai, R., Boross, N., Nyiri, Z. et al. Biliverdin- and protoporphyrin-based eggshell pigmentation in relation to antioxidant supplementation, female characteristics and egg traits in the canary (Serinus canaria). Behav Ecol Sociobiol 70, 2093–2110 (2016).
https://doi.org/10.1007/s00265-016-2214-zHargitai, R. Gergely Nagy, Márton Herényi, János Török. Effects of experimental calcium availability, egg parameters and laying order on Great Tit Parus major eggshell pigmentation patterns Ibis Volume 155, Issue 3 p. 561-570. First published: 18 June 2013
https://doi.org/10.1111/ibi.12054Hargitai, R. Nóra Boross, Zoltán Nyiri, Zsuzsanna Eke. Effects of food limitation on the intensity of blue-green and brown eggshell coloration: an experimental study with the canary. Journal of Avian Biology Volume 49, Issue 1 jav-01486 First published: 15 September 2017
https://doi.org/10.1111/jav.01486Li Z, Ren T, Li W, Zhou Y, Han R, Li H, Jiang R, Yan F, Sun G, Liu X, Tian Y and Kang X (2019) Association Between the Methylation Statuses at CpG Sites in the Promoter Region of the SLCO1B3, RNA Expression and Color Change in Blue Eggshells in Lushi Chickens. Front. Genet. 10:161. doi: 10.3389/fgene.2019.00161
Morales, J., Velando, A. & Torres, R. Biliverdin-based egg coloration is enhanced by carotenoid supplementation. Behav Ecol Sociobiol 65, 197–203 (2011).
https://doi.org/10.1007/s00265-010-1025-xMoreno, J. Elisa Lobato, Judith Morales. Eggshell blue-green coloration fades immediately after oviposition: a cautionary note about measuring natural egg colors. Ornis Fennica 88 (1), 51, 2011.
Navarro, C. Tomás Pérez-Contreras, Jesús M. Avilés, Kevin J. McGraw, Juan J. Soler. Journal of Avian BiologyVolume 42, Issue 6 p. 538-543. Blue-green eggshell coloration reflects yolk antioxidant content in spotless starlings Sturnus unicolor. First published: 30 November 2011
https://doi.org/10.1111/j.1600-048X.2011.05293.xWang, X.T., Deng, C.-J. Zhao, J.-Y. Li, G.-Y. Xu, L.-S. Lian, C.-X. Wu, Study of the Deposition Process of Eggshell Pigments Using an Improved Dissolution Method, Poultry Science, Volume 86, Issue 10, October 2007, Pages 2236–2238,
https://doi.org/10.1093/ps/86.10.2236Wang, X.T., C. J. Zhao, J. Y. Li, G. Y. Xu, L. S. Lian, C. X. Wu, X. M. Deng, Comparison of the total amount of eggshell pigments in Dongxiang brown-shelled eggs and Dongxiang blue-shelled eggs, Poultry Science, Volume 88, Issue 8, August 2009, Pages 1735–1739,https://doi.org/10.3382/ps.2008-00434
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