Modifying MACE to accommodate genomic preselection effects

  • Peter G Sullivan Canadian Dairy Network
  • Esa Mantysaari Natural Resources Institute (Luke)
  • Gerben deJong
  • Haifa Benhajali


Sire evaluations from MACE are used as input for national genomic evaluations. The MACE results are based on traditional evaluation models ignoring genotypes, at both the national and international levels. The exclusion of genotypes is to avoid a cyclical and repeated double-counting of genomic information between national and international systems. Ignoring the genotypes, however, has the consequence of introducing bias in the MACE results, because the effects of genomic preselection are not included in the MACE estimated breeding values of genomically preselected sires. The bias problem is especially relevant for most recent AI bulls, the young sires of most interest in current breeding programs. Current and future methods are discussed, which could be used to reduce genomic preselection biases in MACE, while still generating suitable MACE proofs that can be used as input to national genomic evaluation systems without double-counting the genomic information.