Challenges in selection and breeding of polled and scur phenotypes in beef cattle

摘要

The benefits of polled beef animals in the value chain have become well known and provides an impetus to beef cattle breeders to select for the POLLED gene. Animal welfare is a major concern and polled animals do not need to be subjected to painful dehorning; additional advantages include lower injury risks during transport and improved safety during handling of the animals. The polled condition has been studied over many decades suggesting various modes of inheritance for polled and scur. Since the completion of the bovine reference genome and the advancement of bovine genomics, developments in molecular technology provided additional tools for investigating the genetic basis of the polled and scurs phenotypes. Even though four causal mutations of the POLLED locus have been identified, the molecular basis governing polled/horned condition and the underlying genetics for scurs remains unclear. In this review, a brief overview is provided on the growth and development of horns followed by a discussion on the molecular advancements made over the past two decades in identifying the POLLED gene and associated variants. The identification of the SCURS locus is complicated by the lack of accurate recording of phenotypes for scurs on-farm.