Breeding for polledness has just recently become of interest, since the routinely performed dehorning of calves has raised serious animal welfare concerns. The autosomal dominant inheritance of the polled locus and the availability of a direct gene test have a great potential for a rapid spread of the trait. Nevertheless, it is not clear whether the polled locus influences other traits than horn development as well. In our study, we examined a possible influence of the polled locus on performance traits in Holstein Friesian cattle. For that, we compiled a data set of 1851 Holstein Friesian cows descending from 19 heterozygous polled sires. The genetic horn status of the cows was analyzed and the performances horned and polled daughters were compared using independent two sample t-tests and multi-factor ANOVAs. As phenotypes the routinely estimated breeding values for milk performance, fertility and body conformation were adducted. To investigate a pleiotropic effect, the performances of all polled and horned daughters of the sires were compared. However, the results of the independent two-sample t-test and the ANOVA were inconclusive, contradicting a pleiotropic effect of the polled locus. To compare the performance within the different families a nested ANOVA for multiple factors was used, where the factor genotype was nested within the factor sire. Indeed, we found significant results for the traits yield deviation of milk, fat and protein yield, as well as for the total merit index and the relative estimated breeding values for milk production, protein yield, body, total conformation, fertility, paternal calving traits. Intriguingly, the effect of the polled locus between the different sire groups is partly vice versa. A possible explanation for that is that the polled locus could be linked to putative QTLs influencing those performance traits, but the linkage phases differ between different families. To investigate this more closely we contrive to consider the kinship between the sires in the data set. The exclusion of a pleiotropic effect of the polled locus could reduce the skepticism towards including polledness in the practical breeding strategies. Therewith, breeding for polledness as a non-invasive alternative to dehorning could increase the animal welfare in the cattle industry on a long-term base. Keywords: polled cattle, holstein friesian, milk performance
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Genetic gain - Breeding Objectives and Economics of Selection Schemes 2, , 518, 2018
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