Estimation & Prediction

A Comprehensive GEBV Validation Framework Using Truncated MACE and New Traits in U.S. Dairy Cattle

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Abstract

Genomic estimated breeding values (GEBV) are widely used in dairy cattle breeding programs to support early selection and the international marketing of young bulls, making standardized and transparent genomic validation procedures essential. The Interbull GEBVtest software provides a common framework for assessing bias, dispersion, and predictive performance of genomic evaluations across countries and breeds. Previous studies have shown that validation outcomes are strongly influenced by population size, trait heritability, and temporal consistency between full and truncated evaluations. To address limitations of traditional four-year reference truncation, Truncated Multiple Across Country Evaluation (TMACE) has been proposed as an alternative validation benchmark that applies the contemporary evaluation model while restricting data to a defined historical period. The objective of this study was to evaluate the consistency and predictive reliability of GEBV across U.S. dairy cattle breeds and traits using a TMACE-based validation framework. The analysis was applied to U.S. genomic evaluations from August 2025 and included five dairy cattle breeds-Holstein, Jersey, Brown Swiss, Red Dairy Cattle, and Guernsey-and ten traits spanning production, functional, reproductive performance, health, and calving-related categories. Truncated reference evaluations were constructed using data available through 2021 combined with TMACE output, ensuring methodological consistency between truncated and full evaluations. Validation was conducted using deregressed GEBV, with candidate bull selection following Interbull guidelines. Across breeds, production traits showed the most consistent validation performance, particularly in Holstein and Jersey, with regression slopes close to unity and high coefficients of determination for GEBV. Functional and reproductive traits exhibited greater variability, especially in smaller breeds, where validation was frequently constrained by limited numbers of eligible candidate bulls and elevated standard errors rather than deficiencies in the evaluation models. Gestation length, which transitioned from a national to an international MACE evaluation in August 2025, met validation criteria in Holstein, although validation in other breeds was limited by data availability and small candidate groups. Overall, these results demonstrate that TMACE-based truncated evaluations, combined with the updated GEBVtest software, provide a consistent and flexible framework for genomic validation across breeds and traits, supporting their continued use as evaluation models and international trait portfolios evolve.

Keywords: 2026

How to Cite:

Legarra, A., McWhorter, T., Mota, R., Nicolazzi, E. & Savoia, S., (2026) “A Comprehensive GEBV Validation Framework Using Truncated MACE and New Traits in U.S. Dairy Cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2272941. doi: https://doi.org/10.31274/wcgalp.23414

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