Simultaneous introgression of three POLLED mutations into a synthetic breed of Chinese cattle

The polled phenotype of cattle is increasingly becoming favourable mainly because of the enhanced emphasis on animal welfare, for which the causative mutations have been reported during the past years. The Shuxuan cattle are a new synthetic breed by crossing the indigenous cattle with both Simmental and Holstein semen in Sichuan of Southwest China, in which about 15% of polled individuals have newly emerged. Because official record about POLLED genotypes for the historically imported sires is unavailable, we therefore genotyped the proposed POLLED variants of P-202ID, P-80kbID and P-219ID among 48 polled and 16 horned Shuxuan cattle. It was first revealed that all three candidate mutations have been simultaneously introgressed into Shuxuan cattle, whereas the P-202ID mutation is dominant. Furthermore, one polled animal still remains to carry none of the three candidate mutations, which suggests that further mutation(s) would also exist. Additionally, we sequenced mitochondrial DNA and found that Shuxuan cattle are composed of two matrilineal origins of Bos taurus (65.6%) and B. indicus (34.4%); and there is no origin-biased distribution of polled phenotype. In conclusion, our study first supports the recently reported novel candidate mutation of P-219ID and detects simultaneous presences of all three known POLLED mutations within a cattle breed.