engleski

Genomic analysis of inbreeding depression: Lessons from bull fertility traits

The reduction of the population mean for a quantitative trait such as size, fertility, vigour, yield, and fitness is a negative consequence of inbreeding known as inbreeding depression. For the last 100 years, regression of individual performance on the individual pedigree inbreeding coefficients has been the standard procedure used in majority of research related to human, livestock and plant populations. Derived from the high-throughput SNP information, runs of homozygosity (ROH) were recently proposed as accurate estimates of inbreeding. In this study we estimated inbreeding depression on sperm quality traits in several Austrian cattle populations using inbreeding coefficients derived from pedigree (Fped), genomic inbreeding (ROHs of various length: FROH1 , FROH2 , FROH4, FROH8, and FROH16) and individual multilocus heterozygosity (iH). Bull fertility referred to sperm quality of ejaculates (volume, sperm concentration, percentage of viable spermatozoa and motility) collected in several Austrian Artificial insemination centres. Bulls were genotyped with Illumina Bovine 50k SNP chip. We used mixed model with a bull as a random effect and all other effects (age of the bull, semen collector, month and year of collection and number of ejaculates per bull per day), including pedigree and genomic inbreeding coefficients (covariable), as fixed effects. In majority of models we found the presence of inbreeding depression while the strength of models (pedigree versus genomic inbreeding) interchanged depending on a trait or/and population analysed. On the other side, among all predictors tested, iH was the worst predictor of inbreeding depression. Although, genomic inbreeding coefficients have been shown to be powerful, still much work has left for complete understanding of inbreeding depression.

Inbreeding depression; genomic inbreeding; bull fertility

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