Selective breeding has greatly improved the racing performance of Norwegian-Swedish Coldblooded Trotters over the last 70 years, but it has come at a cost.
Brandon Velie and his colleagues, writing in the journal Genetics Selection Evolution, describe the performance jump in these trotters since the 1950s as remarkable.
“However, this improved racing performance has also been accompanied by a gradual increase in inbreeding level.”
They note that although the breed is not currently considered at risk, it represents a unique Norwegian and Swedish genetic resource and is present on the department of agriculture’s list of horse breeds that should be preserved.
Levels of inbreeding have traditionally been measured using pedigree analysis, but researchers are increasingly applying molecular-based technology to examine the question.
The study team say the industry has shown interest in adopting molecular approaches for the selection and maintenance of the breed.
Because of this, the researchers set out to estimate inbreeding coefficients applying the recent advancements in genomics technology. They then compared the pedigree-based inbreeding coefficients within the breed to the coefficients generated through pedigree analysis.
A total of 566 raced trotters were available for analyses.
Both methods showed a gradual increase in inbreeding level in the breed between 2000 and 2009, they reported. However, genomic inbreeding coefficients were higher than pedigree inbreeding coefficients.
The authors say the upward trend of inbreeding likely warrants additional exploration by the breeding industry, particularly in relation to some differences seen in inbreeding levels between Norwegian-born horses and Swedish-born horses.
They say opportunities exist for the industry to develop programs that provide breeders with easily interpretable feedback on regions of the genome that are suboptimal genetically, or that may prove sensitive to inbreeding within the population.
They say the use of molecular data to identify genomic regions that may be vulnerable to inbreeding problems will likely prove to be valuable for preserving genetic diversity in the long term.
Genomic measures of inbreeding in the Norwegian–Swedish Coldblooded Trotter and their associations with known QTL for reproduction and health traits
Brandon D. Velie, Marina Solé, Kim Jäderkvist Fegraeus, Maria K. Rosengren, Knut H. Røed, Carl-Fredrik Ihler, Eric Strand and Gabriella Lindgren
Genetics Selection Evolution 2019 51:22 https://doi.org/10.1186/s12711-019-0465-7