Comparison of Gene Editing Versus Conventional Breeding to Introgress the Polled Allele into the Tropically Adapted Australian Beef Cattle Population

Abstract

Breeding polled (hornless) cattle is a long-term solution to the costly and increasingly unacceptable cattle management practice of dehorning. This study simulated introgression of the POLLED allele into a tropically adapted Australian beef cattle population via conventional breeding or gene editing for multiple polled mating schemes and compared results to baseline selection on genetic merit using the Japan Ox Economic Index ($JapOx) alone, over the course of 20 years. Overall, our simulations show that given the limited number of polled Brahman sires, conventional breeding to increase the POLLED allele frequency will have to occur gradually to prevent major impacts on the rate of genetic gain. Furthermore, this study demonstrates how gene editing could help to ameliorate these impacts if a rapid decrease in HORNED allele frequency is required due to public pressure or legislation requiring the immediate cessation of dehorning practices.