Future Impact of Molecular Genetics

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Future Impact of Molecular Genetics

• Grant Walling (Roslin Institute)
• John McEwan (AgResearch, NZ)

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Past

• Extensive production
• Varying objectives
• Broad goals hence slower progress
• Localised Breeding

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Present

• Uptake of newer technologies
• Sire Referencing Schemes
• Breeding Values
• Selection Index
• Defined goals
• Wider use of animals with high genetic merit
• Quicker progress towards breeding goals

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Future

• More consumer driven
• Greater efficiency
• Better control over product quality
• Greater use of genetic technology
• Niche markets

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Background

• Most mammalian genes at least partially sequenced
• Human genome sequenced in two years
• Cattle in 5-8 years ?
• Uptake in sheep

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Molecular Genetics What will it deliver ?

• Traceability
• Parent identification/verification
• Use of beneficial genes/QTLs
• New Technologies

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Traceability
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Traceability

• Consumer driven
• Source meat or meat products
• Feedback to producers

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Traceability Consequences

• Requires changes to current procedures
• Many steps affecting processors
• Cost in implementing the system
• Who pays

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Parent Identification/Verification
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Parent Identification/Verification

• Verification simple, identification more
  demanding
• Available now
• Correct pedigree errors
• Source genetic material e.g. Semen

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Use of Beneficial genes/QTLs
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What is a gene?

• An encoding piece of DNA
• Each gene has two alleles
• An animal receives an allele from each parent
• Different alleles alter performance of a gene

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Example Halothane gene in pigs

• Gene controls resistance to malignant hypothermia
• Two alleles N and n
• Three genotypes NN, Nn and nn
• Only Animals with nn genotype are affected
• Genetic test identifies carriers (Nn)

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What is a QTL?

• Quantitative trait locus (QTL)
• Position in the genome associated with a
  quantitative trait
• Gene concerned is unknown

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Example Booroola

• True location unknown
• Booroola test uses approx. 6 markers across the
  known region
• Misclassifications are rare

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QTL Identification

• Use 2 or 3 generation pedigree structure
• Sire reference progeny form large half-sib
  families
• Identify segregation from the sire

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Genes or QTLs

• Genes are more expensive and difficult to detect
• Depends on how information is used
• Genes contribute to understanding of the trait

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Using genes and QTLs

• Improve estimation of breeding values
• Improve performance within flock through marker
  assisted selection (MAS)
• Introgression from another breed/flock to improve
  a different trait

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Improving estimation of breeding values

• Incorporate marker information into evaluations
• Important for genes of large effect

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Marker Assisted Selection (MAS)

• Aim to increase the frequency of favourable
  alleles of a particular gene
• Combine marker information into an existing
  selection index
• Requires optimum weighting of marker information

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Introgression Aim

• Introduce a new alleles to a breed or flock
• Incorporate desirable alleles but minimise donor
  contribution
• Try to maximise the recipient genome

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BC1
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MAS and Introgression What type of traits to use
?

• Growth/Fatness Traits
• Use in MAS, conventional selection very
  successful therefore little use in introgression
• Reproductive Traits
• Wider use, Improvement on conventional selection,
  Benefits from prolific breeds
• Disease Traits
• Large impact, ethically acceptable, rapid
  progress compared to conventional methods

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MAS/Introgression Examples

• Growth/Fatness traits
• Myostatin, Callipyge, Carwell
• Reproduction
• Booroola, Inverdale, Thoka
• Disease Resistance
• QTLs affecting worm burden and facial eczema

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Introgression Drawbacks

• Reduced selection intensity for other traits
• Drag of undesirable characteristics
• Additional management

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Introgression Examples of Drawbacks

• Reduced selection intensity
• Use of animals inferior for commercial traits
• Drag of undesirable characteristics
• Tough meat from callipyge lamb
• Additional management
• Complex flock structure, larger litters

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Real Example Booroola

• Identified in Booroola Merino
• Significant increase in ovulation rate
• Producers wish to use Booroola to increase
  reproductive performance of the Romney

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Real Example Booroola (2)

• Romney Dual purpose breed
• Increasing importance on meat
• Substantial difference between mature size in
  Romney vs. Merino

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Real Example Booroola (3)

• Introgression of Booroola successful
• B animals produce 1.3 corpora lutea more than
  (50 years conventional selection)
• Producers report poor growth from Booroola
  carriers

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Real Example Booroola (4)

• Analysis indicates a gene affecting early growth
  near Booroola (3kg at weaning)
• Approx. 80 of Booroola carriers also inherit low
  growth allele
• Example of linkage drag from the Merino into the
  Romney

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New Technologies
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Genetically Modified Organisms (GMOs)

• Large scale public hype
• Difficult and expensive to produce
• Applications to pharmaceuticals NOT food
• Ethical procedures

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What is a GMO ?

• Animal produced by selective breeding
• Animal with gene introduced from a different
  breed but same species
• Animal with a novel gene introduced (unnaturally)
  from a different species

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Use of GM Livestock

• Currently too expensive
• Poor success rate
• Not acceptable to the public
• More acceptable solutions using conventional
  methods

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Accelerated Genetic Improvement

• Cloning
• Unlikely
• Speed Genetics
• Very Unlikely
• Whizzo Genetics
• More chance of Roslin paying my bar bill

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Summary
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Will Molecular Genetics have an impact ?

• Evidence within the industry
• Parent verification, Scrapie genotyping
• Evidence from other industries
• Pigs, Fish, Dairy Cattle, Poultry
• Address new challenges to progress

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When will it happen ?

• Now
• Scrapie testing
• Soon
• Parentage testing, Traceability, Introgression
  and MAS Disease resistance
• Future
• Introgression and MAS Growth, Fatness, Carcass,
  Reproductive traits

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Which areas will not affect commercial sheep
production?

• GM livestock
• Cloning
• Speed Genetics
• Whizzo Genetics

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What needs to change ?

• Requires input from all sectors
• Cannot be achieved individually
• More co-operation
• Rewards for better animals

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Implications Traceability

• Identification of good and bad post-slaughter
• Opportunity to reward/penalise the good/bad
• Public Safety
• More answerable to product
• geneticists, producers and processors

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Implications Parent Verification

• Product assurance (breed, pedigree etc.)
• Sale of genetics (semen, embryos etc.)
• Decrease in misidentification
• better flock management
• increase in accuracy of breeding values

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Implications Disease Resistance

• Welfare friendly
• Restricted use of animals with no resistance
• Minimum requirements for breeding stock

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Implications MAS

• Increased accuracy of breeding values
• Increased rate of genetic improvement
• Decreased emphasis on individual appearance
• Selling of genetics not animals

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Implications Introgression

• All breeds provide potential source of
  improvement
• Broadens boundaries to improvement
• Increase in management

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Conclusion

• Molecular genetics will impact on sheep breeding
• How can the technology help you?