Molecular genetics applied to animal breeding

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Molecular genetics applied to animal breeding

• Luciana Correia de Almeida Regitano

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Embrapa Southeast Cattle São Carlos - SP
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Embrapa Southeast Cattle

• Stablished in 1975
• 2,668 ha farm
• Forest and reserves 30
• About 3,000 animals

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Current research projects in animal breeding
(genomics highlights)
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• Tropical adaptation traits
• Genome scan in F2 Holstein x Gyr
• Expression profile on tick challenged bovines
• Expression profile on Haemonchus sp. challenged
  bovines
• Candidate genes for endoparasites in ovine
• Meat production and quality traits
• Molecular markers for growth and fat deposition
  in Canchim
• Molecular strategies for improvement of meat
  production and quality of Brazilian beef

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Resistance to tick and tick borne diseases

• Economic losses (tick TBD) U 1.3 billion/year
  (Martinez et al., 2004)
• Influenced by a great number of environmental and
  physiological factors
• Heritabilities ranging from very low to high
  (Alencar et al., 2005).

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F2 Experimental population (1995...)
1999 .... 2006 ? 400 F2

• Phenotypes
• Ectoparasites (Rhipicephalus microplus,
  Dermatobia hominis)
• Endoparasites
• Heat tolerance

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Methods

• No tick control until 10 to 14 months of age...
• Artificial infestations 10,000 R. microplus
  larvae per animal (Groups of 20 to 30 animals)
• Two observations/animal
• Rainy season (October to March N 302)
• Dry season (April to September N 338)

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Results
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Summary of QTL for tick resistance identified on
Holstein x Gyr F2 population (20 chromosomes
scanned)
Season in which ticks were counted Dominance
deviation Proportion of the phenotypic
variance explained by the QTL This QTL was not
tested for dry season data.
Total ?2P Rainy - 13.6 Dry - 11.3
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Next Steps

• Finish genome scan (March)
• Fine map QTL regions
• Validate in commercial populations

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Cytokine expression in resistant animals
5 Naïve Nelore x 5 Challenged Nelore (10,000
larvae)
9th day (nymph modal day) Tissue collection
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Cytokine expression in naïve Nelore

• Ratio of cytokine expression in lymph node
  between challenged and reference group,
  normalized for a constitutive gene (RPL-19).
  Boxes represent the interquartile range, or the
  middle 50 of observations expressed as the
  n-fold differences between groups in relation to
  the control gene. The dotted line represents the
  median gene expression. Whiskers represent the
  minimum and maximum observations

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Molecular markers for growth and fat deposition
in Canchim
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Since 1997...

• Collect DNA sample from all Canchim born at the
  research center
• Till 2005 only weights at different ages were
  available
• Several positive results But phenotypes were not
  the best for MAS!

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2005 Breeding strategies for the improvement of
fat deposition in Canchim

• Ultra-sound evaluation for SF and RYA
• 2005 - 2006
• 572 animals, 2 farms
• Embrapa, Sta. Helena (Goias)
• 2007 (Breeders association involvement!)
• 543 animals, 8 farms, 3 states

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Objectives

• Identify QTLs for meat production and quality
• Validate markers for fat deposition
• Evaluate strategies to include marker information
  on Canchim breeding schemes

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Mixed model analysis for RYA of 987 Canchim
animals from 7 farms, evaluated in 2005, 2006
and 2007.
1No effect on SF or weight at 18 months
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Genetic strategies for improvement of meat
production and quality of Brazilian beef
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World Beef Exports
Source ABIEC - Brazilian Beef Export Industries
Association/USDA
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Meat quality

• Most of Brazilian meat is produced from Nelore or
  crossbred zebu
• Meat tenderness is not the desired for most
  external markets

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Genome scan Candidate genes
X
10 HSF
20 HSF
20 stears / sire
40 stears / sire
Extreme Phenotypes
800 stears / 2008 - 2009

• Feed eficiency
• Carcass
• Meat

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Objectives

• Identify markers useful for selection of meat
  quality traits in the Nelore population

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Research Team
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Thank you! luciana_at_cppse.embrapa.br
Rod. Washington Luis, Km 234 - Fazenda Canchim
C. Postal 339 - CEP 13560-970 - São Carlos - SP
Phone/Fax 55- (16)- 3361 - 5611