Dairy cattle

Aligning U.S. Reproductive Performance Evaluations with Contemporary Dairy Cattle

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Abstract

The Council on Dairy Cattle Breeding publishes reproductive performance evaluations for five breeds, Holstein, Jersey, Brown Swiss, Ayrshire, and Guernsey. The evaluations were first introduced for Daughter Pregnancy Rate (DPR) in 2004, Cow Conception Rate (CCR) and Heifer Conception Rate (HCR) in 2009, and Early First Calving (EFC) in 2019.The goal of this study was to conduct a foundational review of the four U.S. reproductive performance traits to evaluate current relevance given industry changes in reproductive management and data availability as well as explore addition of a new trait, First Service to Conception (FSC). The August 2025 tri-annual evaluation contained 93M (37M) DPR, 45M (19M) CCR, 14M (14M) HCR, 27M (19) FSC, and 37M (37M) EFC records (cows) from the National Cooperator Database. DPR and EFC records are available from 1960 onward, while CCR, HCR, and FSC are available from 2002 onwards based on data collection practices. To evaluate prediction stability for animals from one evaluation to the next, traditional predicted transmitting abilities (PTA) were compared across 7 consecutive evaluations: December 2023, April 2024, August 2024, December 2024, April 2025, August 2025 and December 2025. Several modifications were explored to align reproductive performance evaluations with current management practices. To account for the industry's herd-year application of different voluntary waiting periods (VWP), the DPR formula included a variable VWP conditional on herd-year and lactation group. To account for the industry's individual cow VWP, FSC was investigated. FSC is the number of days from first service to conception and is not a function of VWP. CCR and HCR are functions of successful (1) or unsuccessful (0) inseminations. The individual inseminations are pre-corrected for service sire breed, breeding event type (artificial insemination non-gender select semen, Gender selected semen, natural breeding, or unknown) and days between inseminations. Requiring first lactation cows to be at least 36 months old prior to phenotype inclusion in evaluations reduced bias in young bull PTAs by including information from both high- and low-reproductive performance daughters at the same time. CCR and FSC included a new covariable in their model to account for days in milk at first insemination. In a multi-trait model, FSC was found to be highly genetically correlated with DPR and CCR and moderately genetically correlated with HCR. EFC, a trait included in the current multi-trait reproductive performance model as uncorrelated, was moved to a single-trait model for computational efficiency. New variance components were estimated including the new trait, FSC. Stricter convergence criterion was applied when solving the mixed-model equations for traditional PTA. New criteria were applied to contemporary groups to determine their inclusion. These ongoing developments aim to ensure that U.S. reproductive performance evaluations remain accurate, relevant, and aligned with current dairy industry practices.

Keywords: 2026

How to Cite:

McWhorter, T., Graham, J., Nicolazzi, E., VanRaden, P., Ling, A., Savoia, S. & Legarra, A., (2026) “Aligning U.S. Reproductive Performance Evaluations with Contemporary Dairy Cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285060. doi: https://doi.org/10.31274/wcgalp.23632

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