Estimation & Prediction

A road map to Females in MACE: Current status with Ayrshire data

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Abstract

Interbull's Multiple Across-Country Evaluation (MACE) is a statistical system that integrates national bull genetic evaluations for proven bulls to produce unbiased, internationally comparable estimated breeding values (EBVs). By accounting for cross-country genetic relationships, MACE enables breeders worldwide to identify and use superior sires. The approach enhances prediction accuracy, minimises national bias, and accelerates genetic progress, typically improving EBV reliability. Small reference populations in minor dairy breeds, such as the Ayrshire or Guernsey, constrain the accuracy of genomic predictions and, thereby, genetic progress. To address this challenge, the World Ayrshire Federation launched a global effort to explore prospects for cross-country partnerships. The aim of this study is to adapt MACE to integrate cow EBVs together with the bulls while leveraging the Interbull Data Exchange Area (IDEA) and GenoEx-GDE platforms. The first phase involves adjusting existing IDEA checking programs to include checks on data missingness and distribution, with cow data now incorporated. This phase also entails setting up an IDEA research clone for data reception, harmonising data across different data providers, and ongoing modification of the MACE pipeline to incorporate female data. Data has been gathered via a collaborative call from five countries, including Australia, Canada, Great Britain, South Africa, and the United States of America, for three major production traits: milk, fat, and protein yield. Genotyped cows totalled 9,214, with Canada providing the majority (46%) of the animals. From the submitted data, mean cow reliabilities for the EBVs ranged from 40% for South Africa to 63% in Australia. The next steps will involve further adjustments to the current MACE pipeline, including, but not limited to, updating the current de-regression procedure to correctly handle cows' data, adjusting the MACE model, and investigating any sources of double-counting and potential bias in the results obtained. The development of a female-inclusive MACE represents a major step toward more equitable genomic selection in small and data-scarce populations. This initiative highlights the importance of global cooperation and secure, robust data infrastructures in accelerating genetic gain and ensuring the sustainability of minor dairy breeds.

Keywords: 2026

How to Cite:

Mugambe, J., (2026) “A road map to Females in MACE: Current status with Ayrshire data”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285494. doi: https://doi.org/10.31274/wcgalp.23724

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