Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #382113

Research Project: Improving Dairy Animals by Increasing Accuracy of Genomic Prediction, Evaluating New Traits, and Redefining Selection Goals

Location: Animal Genomics and Improvement Laboratory

Title: Genomic evaluation of crossbred dairy cattle in the United States

item WIGGANS, GEORGE - Council On Dairy Cattle Breeding
item Vanraden, Paul
item Null, Daniel
item NICOLAZZI, EZEQUIEL - Council On Dairy Cattle Breeding
item JANSEN, GERALD - Council On Dairy Cattle Breeding
item MEGONIGAL, JR, JOEL - Council On Dairy Cattle Breeding

Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Genomic evaluations of crossbred dairy cattle were first released in the United States in April 2019 by the Council on Dairy Cattle Breeding (Bowie, MD). Each crossbred animal has an evaluation calculated for each of 5 breeds: Ayrshire, Brown Swiss, Guernsey, Holstein, and Jersey. These evaluations are expressed on an all-breed base and combined by weighting the breed proportions -- called breed base representation (BBR) -- for each animal. The BBRs are estimated with the same process used for other traits. The breed reference populations are updated annually and are composed of AI progeny-tested bulls (at least 10 daughters) with at least 4 generations of same breed ancestry. The blending procedure is applied to animals that have a highest BBR of less than 90%. The SNP effects are estimated from animals with a BBR of at least 94%, which are considered to be purebreds. Evaluations are reported on individual breed bases. In most cases, the breed with the highest BBR is used. However, to facilitate comparisons within herd, the breed associated with an animal’s identification record is used if the BBR is not less than 40%. For weekly evaluations, an initial approximate BBR is calculated based on only the SNPs present on the genotyping chip so that imputation is not required. Currently, 5 groups of chips are defined, and SNP effects for breed determination are estimated for each group. To minimize the portion of animals that are incorrectly designated for blended evaluations based on the approximate BBR, animals with a BBR of at least 85% are processed with purebreds until a BBR based on an imputed genotype is calculated; then animals with a new BBR of less than 90% are moved to the blended group. A breed error is declared if the highest BBR is at least 85% for a breed other than that from the identification record. The blending process is not applied to type traits, which are not comparable across breeds, or to feed saved and calving traits, which are not calculated for all breeds. Recessive traits are not reported for crossbreds because the largely within-breed nature of those traits leads to insufficient reliability in crossbred processing. Crossbred evaluations have lower reliability than those for purebreds, but by processing crossbreds, parentage discovery and BBRs are provided. In February 2021, 131,253 animals had blended evaluations. Of those animals, 22% had been born in 2019, an indication of recent increases in crossbreeding and genotyping of crossbreds.