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Y.-P. Chen, A. Prashar, T. Zayats, J. T. Erichsen, P. M. Hocking, J. A. Guggenheim; The Heritability of Ocular Traits in Chickens From a Layer-Broiler Cross. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1942.
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Refractive error results from a developmental mismatch between the optical power and the size of the eye. Although chickens are a frequently studied animal model of myopia, the role of genetics in determining ocular biometric traits in chickens has been less studied. Our aim was to investigate the heritability of ocular component dimensions in chickens.
Ocular traits were measured in 510 three-week old chickens from the F10 generation of a cross between White Leghorn and broiler lines. High resolution A-scan ultrasonography was used to measure corneal thickness (CT), anterior chamber depth (ACD), length thickness (LT), vitreous chamber depth (VCD) and axial length (AXL). Corneal curvature was assessed by videokeratometry. Equatorial eye diameter and eye weight were measured after enucleation. We used the Relpair v2.0 program to infer the relationships of the chickens, based on 1667 informative single nucleotide polymorphism (SNP) markers. From the intraclass correlation coefficient of the ocular trait values for all full-sib pairs, we calculated the narrow sense heritability under the assumption of no dominance or common environment effects.
Relpair detected 4973 full-sib pair relationships among the 510 chickens. Among the ocular traits, the heritability was highest for VCD (h² = 0.72, 95%CI: 0.67-0.77), followed by AXL (h² = 0.64, 95% CI: 0.59-0.69), corneal curvature (h² = 0.61, 95% CI: 0.56-0.66), LT (h² = 0.58, 95% CI: 0.52-0.63) and eye weight (h² = 0.54, 95% CI: 0.49-0.60). The remaining traits had lower heritabilities (eye diameter, h² = 0.42, 95% CI: 0.36-.47; CT, h² = 0.36, 95% CI: 0.30-0.42; and ACD, h² = 0.36, 95% CI: 0.30-0.41).
All of the ocular traits in chickens had a relatively high heritability, but especially VCD, AXL and corneal curvature, which were similar to heritability estimates of ocular biometric traits in human subjects. The high heritability suggests the potential for quantitative trait locus (QTL) mapping to identify the genes responsible for natural variations in eye size in this layer-broiler cross.
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