title: Heterogeneity in genetic and nongenetic variation and energy sink relationships for residual feed intake across research stations and countries.
abstract: Our long-term objective is to develop breeding strategies for improving feed efficiency in dairy cattle. In this study, phenotypic data were pooled across multiple research stations to facilitate investigation of the genetic and nongenetic components of feed efficiency in Holstein cattle. Specifically, the heritability of residual feed intake (RFI) was estimated and heterogeneous relationships between RFI and traits relating to energy utilization were characterized across research stations. Milk, fat, protein, and lactose production converted to megacalories (milk energy; MilkE), dry matter intakes (DMI), and body weights (BW) were collected on 6,824 lactations from 4,893 Holstein cows from research stations in Scotland, the Netherlands, and the United States. Weekly DMI, recorded between 50 to 200 d in milk, was fitted as a linear function of MilkE, BW0.75, and change in BW (ΔBW), along with parity, a fifth-order polynomial on days in milk (DIM), and the interaction between this polynomial and parity in a first-stage model. The residuals from this analysis were considered to be a phenotypic measure of RFI. Estimated partial regression coefficients of DMI on MilkE and on BW0.75 ranged from 0.29 to 0.47 kg/Mcal for MilkE across research stations, whereas estimated partial regression coefficients on BW0.75 ranged from 0.06 to 0.16 kg/kg0.75. Estimated partial regression coefficients on ΔBW ranged from 0.06 to 0.39 across stations. Heritabilities for country-specific RFI were based on fitting second-stage random regression models and ranged from 0.06 to 0.24 depending on DIM. The overall heritability estimate across all research stations and all DIM was 0.15±0.02, whereas an alternative analysis based on combining the first- and second-stage model as 1 model led to an overall heritability estimate of 0.18±0.02. Hence future genomic selection programs on feed efficiency appear to be promising; nevertheless, care should be taken to allow for potentially heterogeneous variance components and partial relationships between DMI and other energy sink traits across environments when determining RFI.
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
authors.affiliation: Department of Animal Science, Iowa State University, Ames 50011.
authors.forename: D M
authors.initials: DM
authors.lastname: Spurlock
authors.affiliation: Animal and Veterinary Sciences Group, Scottish Agricultural College (SAC), Roslin Institute Building, Easter Bush, Midlothian, EH25 9RG, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Coffey
authors.affiliation: Animal Breeding and Genomics Centre, Wageningen UR Livestock Research, 6700 AH Wageningen, the Netherlands.
authors.forename: R F
authors.initials: RF
authors.lastname: Veerkamp
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 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: Y
authors.initials: Y
authors.lastname: de Haas
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, Agricultural Research Service, USDA, Beltsville, MD 20705.
authors.forename: E E
authors.initials: EE
authors.lastname: Connor
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
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001947:Breeding; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D003612:Dairying / Q000706:statistics & numerical data; D004063:Digestion; D004734:Energy Metabolism; D005260:Female; D014644:Genetic Variation; D040941:Heredity; D009426:Netherlands; D011247:Pregnancy; D012606:Scotland; D014481:United States
keywords: heritability; international study; random regression model; residual feed intake