Comparative Studies of Horned/Polled in Beef and Dairy Cattles

The use of polled genetics is gaining popularity due to economic and safety reasons.  One of the most widely used commercial horned/polled tests is a haplotype test developed in conjunction with Texas A & M University and identifies variation at the polled locus in Bos taurus cattle (beef and dairy).  Recently, two independent, potentially causative mutations of polled, one found in Friesian breeds (Pf) and the other in breeds of Celtic origin (Pc), were reported.  The aim of this study was to compare the original SNP-based haplotype test and the more recent test, for their effectiveness in genotyping Horned/Polled animals by utilizing a large number of animals with known horned or polled phenotypes from various breeds of well-defined pedigrees.  Our results showed almost complete concordance between the SNP based haplotype test and the more recent putative causative mutation test in dairy cattle (Holstein and Jersey).  Furthermore, the SNP-based haplotype test was able to detect both the Celtic mutation and the Friesian mutation in dairy cattle.  A fragment analysis test that is based on the causal mutation of a 212 base pair (bp) insertion/deletion in many Celtic (beef) cattle breeds provides an easier and more effective determination of horned/polled genotype.   In dairy cattle, both tests require a haplotype determination and appear to be equally predictive.