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In the figure 8 above you see the increase in accuracy with increasing size of the reference population for 4 different heritabilities, assuming a q of 500, assuming that the gEBV are estimated using only genomic information. The upper line represents the trait with the highest heritability (0.9), and the lowest that with the lowest heritability (0.05). To achieve the same level of accuracy a decrease in the size of the heritability requires a large increase in the size of the reference population. For example, to achieve an accuracy of 0.6, 5630 are required for traits with heritability of 0.05, whereas only 320 are required for traits with heritability of 0.90. This illustrates that, even though genomic selection is a very nice tool, it is not feasible for small populations, and especially not for traits with a low heritability. As a potential solution, populations (studbooks) could combine forces in composing a reference population, so that they can share the costs, but also the benefits. This is current practice in dairy cattle breeding, where a number of international breeding organisations share a reference population. There is no example that reference populations of different breeds are combined. Theoretical this seems only to be effective when the density of SNP's is very high.Thus:
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The Thus: the size of the reference population can be a imiting factor for achieving accurate gEBV. Solution can be to combine forces across breeding associations. |
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