How Do I Decide What Traits are Important CarcassUltrasound EPDs

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How Do I Decide What Traits are Important?
Carcass/Ultrasound EPDs

• Bob Weaber
• GRA-Cornell Univ. Animal Breeding Group
• rlw26_at_cornell.edu

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Overview

• Which trait should be used in making selection
  decisions?
• Ultrasound or Carcass
• The value of ultrasound records
• Overview of various breed carcass/ultrasound
  genetic evaluations

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Alternate Production Circumstance

• Feedlot owner buying bulls for the production of
  forward contract weanling cattle

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Example Feedlot Goal

• Maximize the income from beef (carcass) less the
  production costs
• Production costs include weanling purchase price
  and per diem feeding costs

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Example List of Traits

• Carcass attributes (eg carcass marbling)
• Ultrasound attributes (eg ultrasound marbling)
• Days to finish

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Example Relative Emphasis

• What is the increase in carcass value from a unit
  change in marbling score, all other traits (in
  the list) held constant ?
• What is the increase in carcass value from a unit
  change in ultrasound score, all other traits
  (such as carcass marbling) held constant ?
• What is the increase in costs from an extra day
  on feed ?

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The Answer

• Ultrasound attributes have no value in themselves
  when the income is determined by the
  corresponding carcass attribute and the
  ultrasound phenotypic measures have been used in
  the multiple trait assessment of carcass
  attributes

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The value of ultrasound records
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Genetic Correlations

• Carcass traits
• Economically relevant
• Observed in fed steer and heifer carcasses
• Ultrasound
• Indicator
• Observed on yearling breeding stock
• Genetic correlation links them
• Want genetic predictors for carcass trait
• Have (most) phenotypes on indicator trait

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Genetic correlations
SE (h2) lt 0.07, SE (Rg) lt 0.13
Crews et al. 2003a
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Why should we use ultrasound data?

• Strong, positive genetic correlations
• Suggests a high proportion of the same genes
  affect both traits
• High heritabilities
• Opportunity for rapid genetic change
• Phenotypic record collection cost
• Carcass 100 vs. Ultrasound 15
• New records (2003)
• Angus 4,290 carcass, 88,167 ultrasound
• Simmental 724 carcass, 4,426 ultrasound

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Relationships
Progeny Carcass Attributes
True Carcass Attribute
Enns, 2003
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Options

• EPD calculated using carcass data
• EPD calculated using ultrasound data
• Carcass EPD calculated using carcass and
  ultrasound data
• Ultrasound data is useful
• Indicator trait

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Does it work?

• Devitt and Wilton (2001) suggested the use of
  yearling bull ultrasound measures for genetic
  improvement of steer progeny carcass traits.
• Selection of high- and low-line IMF phenotype
  sires randomly mated resulted in significant
  differences in progeny USDA QG. (Sapp et al.
  2002)
• Inclusion of ultrasound data in multiple trait
  evaluation improves accuracy of carcass EPD,
  especially for replacements with only an
  ultrasound observation. (Crews and Kemp, 2002
  Crews et al., 2003b)

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Current Carcass/Ultrasound Genetic Evaluations
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Current Genetic Evaluations
Working to incorporate carcass data, Spring 2004
release
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Current Genetic Evaluations
Multi-breed model
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Which EPDs do I use?

• Angus
• Older animals-
• Compare accuracy values from each evaluation
• If very different use EPDs with highest accuracy
• If similar use Carcass EPD given similar
  percentile rank as Ultrasound EPD
• Else, use Ultrasound EPD
• Young animals with own ultrasound observation or
  those with low carcass EPD accuracies
• Ultrasound EPDs
• Other breeds
• Use reported EPDs

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Selected References

• Crews, D. H., Jr. and R. A. Kemp. 2002. Genetic
  evaluation of carcass yield using ultrasound
  measures on young replacement beef cattle. J.
  Anim. Sci. 801809-1818.
• Crews, D. H., Jr., E. J. Pollak, R. L. Weaber, R.
  L. Quaas, and R. J. Lipsey. 2003. Genetic
  parameters for carcass traits and their live
  animal indicators in Simmental cattle. J. Anim.
  Sci. 811427-1433. 242
• Crews, D. H., Jr., E. J. Pollak, R. L. Quaas.
  2003. Evaluation of Simmental carcass EPD
  estimated using live and carcass data. Submitted
  J. Anim. Sci.
• Devitt, C. J. B, and J. W. Wilton. 2001. Genetic
  correlation estimates between ultrasound
  measurements on yearling bulls and carcass
  measurements on finished steers. J. Anim. Sci.
  792790-2797.
• Sapp, R. L., J.K. Bertrand, T. D. Pringle, and D.
  E. Wilson. 2002. Effects of selection for
  ultrasound intramuscular fat percentage in Angus
  bulls on carcass traits of progeny. J. Anim. Sci.
  802017-2022.
• Wilson, D. E. 1992. Application of ultrasound for
  genetic improvement. J. Anim. Sci. 70973-983.