Frequency and Repeatability of Recombination Rates in Beef Cattle

Research at the Cooperative Research Centre for Beef Technologies over the last 18 years has resulted in genotyping over 11000 cattle from a variety of breeds using a mixture of high and low density SNP tests. After a stringent quality assurance process, sire haplotypes were inferred from progeny genotypes and sire genotypes where available, and haplotypes determined for progeny. Numbers of recombinations in each progeny's sire gamete were calculated for each chromosome and the total for each individual. Over 250 small to medium sized half-sib families were available. Total recombinations per individual were analysed with a sire model to ascertain the repeatability of recombination rate. There were an average of 0.4 to 1.7 recombinations per chromosome, proportional to the length of the chromosome. The frequency of inheritance of a complete chromosome, without recombination, ranged from 0.2 to 0.6 and was inversely proportional to its length. The average number of recombinations per gamete was 21, with modest variation among breeds. The repeatability of recombination was estimated from a subset of the data with families of 10 (5) half-sibs as 0.25 (0.30). The low frequency of recombinations per gamete means that accurate haplotypes for progeny can be imputed from low density genotypes if the haplotypes of one parent are available.