Genomic Inbreeding Score

Identify the true level of inbreeding by analysing the number of duplicate genetic variants that have been inherited from the sire and dam.

Plusvital’s researchers analysed a cross-section of the Thoroughbred population to determine the highest and lowest levels of inbreeding that exist. The study cohort of over 2,000 Thoroughbred horses from Europe, Australasia and USA, including 704 unique sires and 1,261 unique dams, provided genome-wide information on 70,000 different genetic variants to identify the range of inbreeding.

Utilising this data, the Genomic Inbreeding Score can definitively identify the actual level of genetic inbreeding in a Thoroughbred horse which can be used to inform future mating decisions. Each horse is ranked as Low, Medium or High for genomic inbreeding.

A high score means that the individual has a significantly higher than expected number of variants that are identically derived from both parents (i.e. homozygous).

Importantly, it was found that while pedigree is generally a good indicator of expected level of inbreeding, it may also be misleading, as the table below for eight stallions shows. This could have important consequences for future breeding decisions and may provide support for alternative breeding options.

Stallion W appears to have a high level of inbreeding based on pedigree, but genetically has a low number of identical gene variants (homozygosity). Stallion S appears to have a low level of inbreeding based on pedigree, but genetically has a very high number of identical gene variants and is very inbred.


Examples of differences between pedigree inbreeding and genomic inbreeding.

Stallion Genomic
Inbreeding Score
Duplicates in 5
generation pedigree
AW Low 4
Z Low 2
W Low 8
AM Low 2
R High 6
S High 0
AR High 8
FM High 3
Genomic Inbreeding Score €225 £185 AUS $275 US $275

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Plusvital is able to accept DNA samples from almost all bloodstock regions within the world. The process is simple and involves a 4-5ml uncoagulated blood sample from each horse in a purple cap K2-EDTA tube. If you require any assistance or advice, please contact us directly.

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