title: An alternative approach to modeling genetic merit of feed efficiency in dairy cattle.
abstract: Genetic improvement of feed efficiency (FE) in dairy cattle requires greater attention given increasingly important resource constraint issues. A widely accepted yet occasionally contested measure of FE in dairy cattle is residual feed intake (RFI). The use of RFI is limiting for several reasons, including interpretation, differences in recording frequencies between the various component traits that define RFI, and potential differences in genetic versus nongenetic relationships between dry matter intake (DMI) and FE component traits. Hence, analyses focusing on DMI as the response are often preferred. We propose an alternative multiple-trait (MT) modeling strategy that exploits the Cholesky decomposition to provide a potentially more robust measure of FE. We demonstrate that our proposed FE measure is identical to RFI provided that genetic and nongenetic relationships between DMI and component traits of FE are identical. We assessed both approaches (MT and RFI) by simulation as well as by application to 26,383 weekly records from 50 to 200 d in milk on 2,470 cows from a dairy FE consortium study involving 7 institutions. Although the proposed MT model fared better than the RFI model when simulated genetic and nongenetic associations between DMI and FE component traits were substantially different from each other, no meaningful differences were found in predictive performance between the 2 models when applied to the consortium data.
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing 48824.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing 48824.
authors.forename: M J
authors.initials: MJ
authors.lastname: Vandehaar
authors.affiliation: Department of Animal Science, Iowa State University, Ames 50011.
authors.forename: D M
authors.initials: DM
authors.lastname: Spurlock
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: K A
authors.initials: KA
authors.lastname: Weigel
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: L E
authors.initials: LE
authors.lastname: Armentano
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville 32611.
authors.forename: C R
authors.initials: CR
authors.lastname: Staples
authors.affiliation: Animal Genomics and Improvement Laboratory, USDA Agricultural Research Service, Beltsville, MD 20705.
authors.forename: E E
authors.initials: EE
authors.lastname: Connor
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5 Canada.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Statistics, Kansas State University, Manhattan 66506.
authors.forename: N M
authors.initials: NM
authors.lastname: Bello
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing 48824. Electronic address: tempelma@msu.edu.
authors.forename: R J
authors.initials: RJ
authors.lastname: Tempelman
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D002149:Energy Intake; D005260:Female; D008957:Models, Genetic; D010641:Phenotype; D015203:Reproducibility of Results
keywords: Cholesky decomposition; feed efficiency; multiple trait model; residual feed intake