miniature bull terriers: breeding strategies for health dr sarah blott
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Miniature Bull Terriers: Breeding Strategies for Health Dr Sarah Blott. Animal Health Trust The science behind animal welfare. TOOLS to aid breeding decisions. BREEDING PROGRAMMES for long-term health. General health Management of genetic diversity Optimised breeding programmes - PowerPoint PPT PresentationTRANSCRIPT
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Miniature Bull Terriers:
Breeding Strategies for Health
Dr Sarah Blott
Animal Health TrustThe science behind animal welfare
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TOOLS to aid breeding decisions
Single gene diseases
DNA tests
Complex diseases
Estimated Breeding Values (EBVs)Genomic BVs (based on DNA)
Mate selection program
BREEDING PROGRAMMES for long-term health
General health
Management of genetic diversity
Optimised breeding programmes
Reduce or eradicate known disease and maintain long-term health
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Overview
• Gene pool and genetic diversity
• Inbreeding
• Approaches to minimising diversity loss
• Current situation in the MBT
• Future breeding strategies
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Gene pool and genetic diversity
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Gene pool and genetic diversity
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Inbreeding
Inbreeding coefficient
Coancestry/kinship
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Inbreeding coefficient
1/2
1/2
1/2 1/2
1/2
1/2
(1/2)6 = 0.0156
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Genetic bottlenecks
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Diversity loss
• High risk factor for emergence of new inherited disease
• Long-term health means managing the loss of diversity
• Controlling the rate of increase of inbreeding
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Control of inbreeding
• What is the end goal?
• Constrain rate of inbreeding (ΔF) to no more than 0.5% per generation
• Effective population size (Ne)= 100 At least!
• If below this, fitness of the population will steadily decrease and population will become unviable in the long-term
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Possible approaches
• Minimising coancestry (kinship) of matings
• Increasing numbers of animals used for breeding
• Equalising the use of males and females
• Optimising genetic contributions
• Inter-breeding
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Miniature Bull Terrier
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Number of KC registrations
4,110 dogs 354 sires 797 dams
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Number of sires and dams used
Mean no. sires = 18.7Mean no. dams = 33.2Ratio = 1.72 dams/sire
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Ratio of dams/sires
1981
1993
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Percentage dogs used for breeding
15% males become sires40% females become dams
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Observed and expected inbreeding
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Effective population size (Ne)
% per generation Ne Registered/year
MBT 1.1 48 203
IRWS 1.8 28 133
CKCS 0.4 123 11,903
Labrador 0.5 103 26,757
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Number of offspring per sire/dam
SiresMean no. offspring = 13.7
DamsMean no. offspring = 5.6
4 sires > 100 offspring15 dams > 20 offspring
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Population relationships
MBT born between 2006-2008
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Conclusions
• scope for improvement
• minimising coancestry (kinship) of matings
• optimum contributions (no. of offspring)
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PLL
• approx. 1200 dogs of breeding age in UK
• genotype all possible dogs and re-select breeding individuals?
• breed with carriers for one further generation and select unaffected homozygote (normal) replacements
• further analysis based on pedigree and genotyping results
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Inbreeding coefficient Kinship coefficients
Rosedawn Delilah 0.04 Ballymore Delight 0.02Ballymore Samson 0.01Legend of Kilkenny 0.02Rosedawn Diamond 0.12Lordswood Romancer 0.08
Recommended
http://www.the-kennel-club.org.uk/services/public/health/search/Default.aspx
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Acknowledgements
• Dr Tom Lewis (KCGC at the AHT)
• Dr Jeff Sampson (The Kennel Club)