Improving Accuracy of Genetic Selection through Incorporation of Genomics
Dr. Pius B. Mwansa, Ph.D.,
Modern breeds of livestock emerged from pre-existing regional animals in the late 18th through the 19th century. In those days, it was generally believed that observed differences between known breeds of livestock were a result of influences of localized environmental effects than an inherent property of the animal that we now know as genetic effects. Eventually a period of livestock breeding was born from the realization that planned breeding could lead to fixation of desired characters in domestic animals. Works by early notables such as Robert Bakewell, Charles Darwin and that of the Austrian monk Gregor Mendel contributed greatly to the body of genetic improvement knowledge we have today. Nowadays, in livestock genetic improvement programs, we employ methods and tools introduced and explained by Dr. C. R. Henderson in the1950’s. This approach is now proudly known as the animal model which relies on pedigree relationships for genetic evaluation. While the application and use of animal model methods in estimating breeding values (EBVs) has served the animal genetic improvement industry well, new genomic approaches have demonstrated even greater enhanced accuracy of selection for economically important traits. A number of procedures for genomic selection have been proposed and their relative merits discussed by many experts in this field (e.g. VanRaden, 2008, Aguilar, et al. 2010 and Misztal et al., 2013). Genomic evaluation relies on the identification and use of specific regions of the pigs’ chromosomes that affect variation in traits affecting producer profitability. Methods for rapidly searching for such regions continue to be developed and improved. Genomic evaluation methods combine traditional phenotype and pedigree information with genomic information to produce genomic estimated breeding values (GEBV) for selection. Genomic estimated breeding values have benefits such as a) increased accuracy of breeding values b) combining own information on young animals for traits measured later in life (e.g. reproduction) or not expressed at all (e.g. litter size for boars), c) enhanced selection programs through quicker turn-over of generations and d) reduced rate of inbreeding per generation. Currently a number of software programs are available for the implementation of routine genomic evaluations of economically important traits in many livestock species including swine. Genesus has directed significant investment dollars to R&D studies to identify genomic variants in traits currently in our animal model selection program. Genome-enabled selection is the future of our industry and Genesus is taking full advantage of this emerging technology to drive increased genetic improvement. References Aguilar, I., I. Misztal, D. L. Johnson, A. Legarra, S. Tsuruta, and T. J. Lawlor. 2010. A unified approach to utilize phenotypic, full pedigree, and genomic information for genetic evaluation of Holstein final score. J. Dairy Sci. 93:743-752. Misztal, I., S. E. Aggrey, and W. M. Muir. 2013. Experiences with a single-step genome evaluation. Poultry Science 92:2530-2534. VanRaden, P. M. 2008. Efficient methods to compute genomic predictions. J. Dairy Sci. 91:4414-4423.