Breeding goals & design

Comparison of trait weighting and relative emphasis between U.S. beef x beef and beef x dairy breeding objectives

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Abstract

The use of beef semen in dairy herds to produce beef x dairy (BxD) terminal offspring has increased in the United States, creating a need for selection tools to rank beef bulls for use on dairy cows. The objective of this study was to compare trait weighting and relative emphasis between BxD and beef x beef (BxB) economic selection indexes and breeding objectives. Indexes were constructed using the Beef Improvement Federation implementation of iGENDEC to simulate economic outcomes. Six crossbreeding systems were evaluated: four BxD (Angus x Holstein, Angus x Jersey, Limousin x Holstein, Limousin x Jersey) and two BxB (Angus x Angus-Hereford, Limousin x Angus-Hereford). Traits included in the breeding objective were hot carcass weight (HCW), ribeye area (REA), fat depth (FAT), marbling score (MS), feed intake (FI), and calving ease; BxB indexes additionally included weaning weight and yearling weight. Marginal economic values (MEVs) and relative emphasis (RE) were calculated for each trait to quantify their weight within the indexes and relative impact on breeding objectives. Six scenarios were investigated to quantify sensitivity to average HCW, days on feed (DOF), and carcass weight discounts. The scenarios investigated were: breeding system and breed of sire specific phenotypic means (Scenario 1), assumed mean HCW of 397 kg across all systems (Scenario 2), mean HCW of 397 kg and reduced DOF for BxD (Scenario 3), increased mean HCW to 454 kg (Scenario 4), mean HCW of 454 kg with reduced DOF for BxD (Scenario 5) and scenario 5 with no HCW heavy-weight discount (Scenario 6). Breeding objectives that assumed Angus sires had larger average RE for REA (0.054 vs 0.047) and smaller average RE for MS (0.126 vs 0.156) compared to objectives that assumed Limousin sires. Scenarios 4 and 5 had the lowest average RE for HCW (0.235 and 0.246) compared to other scenarios ( >0.307). Averaged over breeding systems and sire breeds, as mean HCW increased, MEVs for MS and REA increased, FAT MEVs became more negative, and the MEV for HCW decreased given the assumed heavy weight discount. Removing the heavy-weight discount increased average HCW RE from 0.246 to 0.340 and, consequently, the RE for other traits decreased. When DOF decreased, MEVs for FI became less negative and RE for HCW, FAT, and MS increased while the RE for FI decreased. Beef x dairy systems had larger MEVs for FI (negative), REA, and HCW and smaller MEV for MS as compared to BxB. For BxD, average RE were substantially larger for FI (0.386 vs 0.246) and smaller for MS (0.128 vs 0.167) as compared to BxB. Differences in trait weighting across systems indicate that applying BxB indexes to BxD production systems would over-emphasize MS and under-emphasize FI, HCW and REA.

Keywords: 2026

How to Cite:

Golden, B., Meier, L., Newman, S. & Spangler, M., (2026) “Comparison of trait weighting and relative emphasis between U.S. beef x beef and beef x dairy breeding objectives”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2283496. doi: https://doi.org/10.31274/wcgalp.23503

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