engleski

Genomic dissection of inbreeding depression: Lessons from the bull fertility traits

Regression of performance (phenotype) on the individual pedigree inbreeding coefficients has been the standard procedure used to quantify inbreeding depression in humans and animals. In Austrian Fleckvieh bulls we have estimated inbreeding depression for the sperm quality traits (volume, sperm concentration, percentage of viable spermatozoa and motility) with emphases on the comparison of models based on pedigree inbreeding versus models based on various genomic estimates of inbreeding (BovineSNP50 BeadChip). Furthermore, we also analyzed models with chromosomal inbreeding coefficients (1 to 29) as well as models with combination of several chromosomal inbreeding coefficients. Mixed models were used 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 or genomic inbreeding coefficients (covariable) as fixed effects. Inbreeding depression was found for the volume and percentage of viable spermatozoa, although between two artificial insemination centres some results were heterogeneous. In general, models based on pedigree were comparable to models based on genomic inbreeding (runs of homozygosity) while models based on individual heterozygosity were inferior. In contrast, for all traits analyzed, models with various chromosomal inbreeding coefficients outperformed models based on overall genomic inbreeding as well as models based on pedigree. However, while genomic inbreeding coefficients have been shown to be powerful, still much work has left to complete our understanding on architecture of inbreeding depression.

Inbreeding depression; genomic inbreeding; bull fertility

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