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Molecular genetics applied to animal breeding

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Title: Molecular genetics applied to animal breeding


1
Molecular genetics applied to animal breeding
  • Luciana Correia de Almeida Regitano

2
Embrapa Southeast Cattle São Carlos - SP
3
Embrapa Southeast Cattle
  • Stablished in 1975
  • 2,668 ha farm
  • Forest and reserves 30
  • About 3,000 animals

4
Current research projects in animal breeding
(genomics highlights)
5
  • 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

6
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).

7
F2 Experimental population (1995...)
1999 .... 2006 ? 400 F2
  • Phenotypes
  • Ectoparasites (Rhipicephalus microplus,
    Dermatobia hominis)
  • Endoparasites
  • Heat tolerance

8
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)

9
Results
10
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
11
Next Steps
  • Finish genome scan (March)
  • Fine map QTL regions
  • Validate in commercial populations

12
Cytokine expression in resistant animals
5 Naïve Nelore x 5 Challenged Nelore (10,000
larvae)
9th day (nymph modal day) Tissue collection
13
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

14
Molecular markers for growth and fat deposition
in Canchim
15
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!

16
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

17
Objectives
  • Identify QTLs for meat production and quality
  • Validate markers for fat deposition
  • Evaluate strategies to include marker information
    on Canchim breeding schemes

18
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
19
Genetic strategies for improvement of meat
production and quality of Brazilian beef
20
World Beef Exports
Source ABIEC - Brazilian Beef Export Industries
Association/USDA
21
Meat quality
  • Most of Brazilian meat is produced from Nelore or
    crossbred zebu
  • Meat tenderness is not the desired for most
    external markets

22
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

23
Objectives
  • Identify markers useful for selection of meat
    quality traits in the Nelore population

24
Research Team
25
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
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