Abstract
BackgroundBreeding genetically hornless, i.e. polled, cattle provides an animal welfare-friendly and non-invasive alternative to the dehorning of calves. However, the molecular regulation of the development of horns in cattle is still poorly understood. Studying genetic characters such as polledness and scurs, can provide valuable insights into this process. Scurs are hornlike formations that occur occasionally in a wide variety of sizes and forms as an unexpected phenotype when breeding polled cattle.MethodsWe present a unique dataset of 885 Holstein–Friesian cattle with polled parentage. The horn phenotype was carefully examined, and the phenotypic heterogeneity of the trait is described. Using a direct gene test for polledness, the polled genotype of the animals was determined. Subsequently, the existence of a putative scurs locus was investigated using high-density genotype data of a selected subset of 232 animals and two mapping approaches: mixed linear model-based association analyses and combined linkage disequilibrium and linkage analysis.ResultsThe results of an exploratory data analysis indicated that the expression of scurs depends on age at phenotyping, sex and polled genotype. Scurs were more prevalent in males than in females. Moreover, homozygous polled animals did not express any pronounced scurs and we found that the Friesian polled allele suppresses the development of scurs more efficiently than the Celtic polled allele. Combined linkage and linkage disequilibrium mapping revealed four genome-wide significant loci that affect the development of scurs, one on BTA5 and three on BTA12. Moreover, suggestive associations were detected on BTA16, 18 and 23. The mixed linear model-based association analysis supports the results of the combined linkage and linkage disequilibrium analysis. None of the mapping approaches provided convincing evidence for a monogenic inheritance of scurs.ConclusionsOur results contradict the initial and still broadly accepted model for the inheritance of horns and scurs. We hypothesise an oligogenetic model to explain the development of scurs and polledness.
Highlights
Breeding genetically hornless, i.e. polled, cattle provides an animal welfare-friendly and non-invasive alternative to the dehorning of calves
Observed phenotypes were classified into five categories: (i) “smoothly polled”: absence of horns or any corneous growth in the horn area; (ii) “small frontal bumps”: small bulges in the horn area that are probably due to ossification; (iii) “frontal bumps”: pronounced bulges in the horn area and no keratinization of the skin; (iv) “scurs”: hornlike formations in the horn area that are loosely attached to the skull by soft tissue and that vary from frontal bumps with a keratinization of the covering skin to long hornlike formations; and (v) “horns”: regular horns that are firmly attached to the skull
For the remaining 10 individuals, we were not able to unambiguously state the horn phenotype and these were classified as others
Summary
I.e. polled, cattle provides an animal welfare-friendly and non-invasive alternative to the dehorning of calves. Gehrke et al Genet Sel Evol (2020) 52:6 conducted, and rapidly, polledness was described as an autosomal dominant trait These studies reported the unexpected occurrence of scurs in polled cattle. Scurs are described as hornlike formations that grow in the same area as horns and are only loosely attached to the skull [5, 6] It is not clear at what age scurs develop, but they are assumed to occur later in life than horns [7]. The occurrence of scurs hampers the advantages that could be achieved by breeding for polledness as they bear an injury risk and make dehorning necessary again They could be perceived as an anomaly leading to an uncertain inheritance of polledness and, in practice, decrease the acceptance of diffident farmers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
