The Coldblooded trotter has successfully been bred for trotting performance, and the intense selection has led to a rapid increase not only in genetic merit but also in relatedness and inbreeding. This project aims to increase our knowledge about inbreeding depression in Coldblooded trotters to provide a basis for sustainable breeding choices. So far in the project, we have estimated inbreeding effects on performance traits and career length, while analysis of fertility traits is ongoing. We have purchased SNP arrays for genotyping and started genotyping breeding stallions. Additional samples will be collected to complement these, together with already existing genotypes. Two young researchers have been recruited for the project. Further, we continue the work aiming to detect signatures of deleterious and lethal alleles at high frequency in the population, and devise and communicate strategies to manage inbreeding in the breed.
Norwegian-Swedish Coldblooded trotters are successfully bred for trotting performance. Intense use of popular stallions has led to a rapid increase in relatedness and inbreeding, and an effective population size of around 50. This implies a risk of inbreeding depression and previous studies showed that this small native population is prone to negative effects of inbreeding. Preserving the health and robustness of the breed by managing inbreeding and genetic defects is important for its popularity, for the trotting industry’s ‘social license to operate’, and the economy of horse owners.
We aim to estimate effects of inbreeding on performance, longevity, and fertility traits, detect signatures of deleterious and lethal alleles at high frequency, and devise strategies to manage inbreeding and deleterious alleles. We hypothesize that inbreeding negatively influences performance and fertility in Coldblooded trotters, that there are ancestor specific effects of inbreeding, and that deleterious alleles segregating at high frequency can be identified and thus better managed in the population. We will work with field data and genotype information in four work packages;
WP1: estimate effects of pedigree inbreeding on performance and fertility traits in linear mixed models, including specific inbreeding effects of highly contributing ancestors.
WP2: select 700 horses for SNP-genotyping from hair samples, to be combined with 600 existing genotypes.
WP3: detect candidate lethal alleles by identifying haplotype homozygote deficiency and identify candidate deleterious alleles with negative effects on performance by genome-wide association studies on homozygosity identified as runs of homozygosity.
WP4: disseminate results and their implications both scientifically and in popular scientific form to the industries.
