Breeding Objectives for Terminal Sires

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Breeding Objectives for Terminal Sires
Michael MacNeil USDA ARS Miles City, MT
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Acknowledgements

• John Stewart-Smith
• Scott Newman
• William Herring
• Larry Benyshek

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Single-Trait EPD or EBV

• Predicts heritable differences among animals for
  individual traits

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Do EPD and EBV work?
Milk EPD, peak yield, and total milk production
from Line 1 Hereford cows Milk EPD, kg Peak,
kg/d Total, kg -10 5.0 697 - 5
5.9 819 0 6.8 940 5
7.7 1062 10 8.5 1183
YES!
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Animal Improvement Systems
What to change
Goal
What to measure
Breeding Objective
Selection Criteria
What is net worth of change
Who to measure
Economic Analysis
Breeding SchemeDesign
Mating Plan
Dissemination System
What to do with good ones
Garrick
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GeneticMerit
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EPD / Acc
EPD / Acc
Difference
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Commercial Producers

• Capture heterosis
• 25 increased output
• 3 increased input
• gt100/cow/year increased net return
• Use complimentary
• Locally adapted maternal breeds
• Terminal sires

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Objective

• Discuss derivation of breeding objectives for
  terminal sires

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Sire Selection
It is always about predicting the future!
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Model production system
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Phenotypes

• Reproduction Pregnancy rate and calf
  survival
• Growth Direct and maternal effects
  preweaning
• direct effects postweaning
• Feed Intake Cow herd (size and milk) and
  feedlot
• Carcass Multivariate normal distribution
• weight, marbling and cutability

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Breeding Systems

• Straightbred Angus females
• Angus, Simmental
• 2-breed rotation females
• British x British Limousin, Charolais
• British x Continental Hereford

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Economics

• Monitor costs for cow-calf and feedlot phases of
  production
• Derive returns from carcass beef with price
  discrimination based on carcass merit

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Economically Relevant Traits

• Sensitivity analysis to determine traits of
  terminal sires that affect profitability of
  production system
• Economically relevant traits (ERT) are those that
  change profit

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Means of traits of economic importance in
selection of terminal sires
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Post-weaning Management
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Basis of price discrimination among Angus sired
carcasses
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Basis of price discrimination among Charolais
sired carcasses
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Basis of price discrimination among Hereford
sired carcasses
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Basis of price discrimination among Limousin
sired carcasses
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Basis of price discrimination among Simmental
sired carcasses
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From model to breeding objective
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Calculations

• Determines partial derivative (d) of profit with
  respect to each ERT
• Breeding objective
• H ? diGi after Hazel (1943)
• I ? diEBVi Henderson (1951)

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Breeding objectives for terminal sires
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Economic values relative to genetic variation
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Correlations between objectives
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EPD / Acc
EPD / Acc
Difference
Index 4
Index 4
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Complications in application

• Not all ERT have EPD or EBV
• Map ERT onto EPD or EBV following Schneeburger et
  al., 1992
• Variation among production systems
• Substantial correlations among objectives for
  terminal sires across somewhat different
  production systems

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Change is inevitable, adaptability and survival
are optional
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Thank-you!