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Breeding Jersey cattle for Africa in the era of genomics
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Transcript of Breeding Jersey cattle for Africa in the era of genomics
Breeding Jersey cattle for Africa in the era of genomics
Prof Norman Maiwashe1,2 (PhD, Pri. Sci. Nat)
1ARC-Animal Production InstitutePrivate Bag X2
Irene 0062
2University of the Free StateP.O. Box 339
Bloemfontein 9300
20th International WJCB Conference , Western Cape, South Africa, 17 Sept 2014
Presentation Outline
• A breeder’s dilemma – Inbreeding versus Genetic progress
• How will genomics:– Complicate or Simplify breeding
• Summary
Genetic Improvement is a balancing act
Minimal Inbreeding
Rapid Genetic Progress
The curse is in the principle!– Superior animals (sires) are provided more breeding
opportunities
While:
– Inferior animals (sires) are denied breeding opportunities
Consequently:• Most of the progeny are from few outstanding sires and
are «likely to be outstanding themselves»
• When this progeny in turn become parents, they are more «likely to mate with their siblings»
Question 1:
Is the rate of inbreeding reaching critical levels in Jersey populations?
Inbreeding level in SA dairy cattle
Inbreeding level in SA Jersey 4.8%
Du Toit et al. (2012)
Inbreeding in Canadian Jerseys
Du Toit et al. (2012)
Inbreeding depression
• Inbreeding has a negative impact on longevity in SA Jersey cattle (Du Toit et al., 2012)
-0.14%
Mean longevity
-0.35%-0.22%
Lact. 1 Lact. 2 Lact. 3
A 1% increase in inbreeding is associated with ~0.5% reduction in longevity
Inbreeding in the genomic era• ΔF will increase due to shorter rapid generation interval
• Management of inbreeding will become more important
• Opportunity – Genomics may allow for new ways to control inbreeding
e.g. use of DNA to calculate genomic relatedness and inbreeding
Answers to Question 1:
• Inbreeding is real and should be managed– Use superior bulls that are less related to the population
• Genomics could lead to rapid inbreeding – but offer better tools for managing inbreeding (genomic mating
programs)
• Remember: Inbreeding is not bad per se – it is rapid inbreeding that is bad
• Mild inbreeding with intense selection is good
Question 2:
How was the Jersey breeder’s life before genomics?
Genetic trend for Calving Interval
Conformation and Udder TraitsFigure: Genetic trends for « conformation » and « udder » in SA Jersey
Theron et al. (2012)
Answers to Question 2
How was the Jersey breeder’s life before genomics?
Answer:• Good genetic progress made on measured traits (often
with high h2) albeit at a relatively slow pace
• Little progress on lowly heritable traits
• Progress was costly (time and money)
Question 3
How is the Jersey breeder’s life during genomics?
Genomic opportunities
1. Genomics for managing deleterious haplotype carriers (e.g JH1, JH2 and Fertility 1)
– Decreased reproductive efficiency (is accessible to the breeder)
2. Genomic selection (more about this later)– Selection of young animals with DNA test (with
reasonable reliability ~60%)
3. Parentage verification or discovery of missing ancestors (is accessible to the breeder)
Genomic selection• Requires a large number of animals with accurate proofs
e.g. >1000 animals
• Genotyping costs are still high – Use of cows in the reference population is a possibility– Genotyping a small group of animals with high density chips and
using imputation
• Important question: – Can I use genomic proofs from another country?
• Answer: – Advise: tread carefully– Genomic proofs are population-specific and their reliabilities may
erode in a different population• Using foreign scale could be hazardous for traits with low international
genetic correlations (Partry and Ducrocq, 2014)
Priorities during the Genomic Era
• Genomic exploitation strategy:– High value animals (influential)
• genotype with 50K or higher density SNP chip
– Low value animals • genotyped using low density chips for:
– Parentage verification – Genomic inbreeding – Deleterious haplotypes
The KEY to genomic selection
• Aggressive data collection (milk/performance recording)
• What kind of data?– Fertility– Adaptation to heat stress– Weights / growth– Feed efficiency – Methane production– Health
Answer to Question 3
How is the Jersey breeder’s life during genomics?
Answer?• Genomics for parentage verification and managing
deleterious haplotypes is a reality and beneficial
• Genomics proofs presented on foreign scale should be treated cautiously
Summary• Inbreeding is a threat to long-term genetic improvement
and should be managed
• Genomics presents an opportunity for fast-tracking genetic improvement
• More emphasis should be placed on:– collection of data on traits that are difficult to improve through
conventional selection
• Both public and private (industry) investment is key to exploitation of genomics selection
Thank You Dankie vir u andaag
Ndi a livhuwa