Maximising the Rate of Genetic Gain in Cattle through Embryonic Genotyping

Progeny-testing of adults has been the foundation of genetic gain in NZ dairy farming since the 1950s. In spite of its success, progeny-testing remains costly in terms of time (6 years per cycle) and money. Due to the increasing demand for dairy products, maintaining and accelerating the rate of genetic gain is of high priority in order to maximise productivity. While the introduction of genotyping young animals using single nucleotide polymorphisms (SNPs) is now allowing genetic gain to occur without the need for extensive phenotyping of their progeny, the 9 month gestation period remains costly. By integrating advanced reproductive and genomic technologies, selection intensity amongst bovine embryos can be increased and rate of genetic gain accelerated.  One strategy for maximising genetic gain is through the production of embryos from genetically superior parents using in vitro fertilisation with subsequent identification of genetically superior embryos which may then be transferred into recipient cows. For this technology to be successful, it is imperative that genotyping data generated from the small number of cells biopsied a few days after fertilisation, provide enough DNA for accurate and precise interrogation with SNP chips and reflect the true genotype of the resulting calf.  Here we present data from genotyping embryo biopsies using an Illumina 50K BeadChip, and how accurately these genotypes predicted sex and genotype of the resulting calf, together with the role of imputation in this process. We also discuss whether this approach presents a feasible, cost effective method for accelerating genetic improvement in dairy cattle.