Summary
Samenvatting Genetic Improvement of Livestock
- Course
- Institution
Samenvatting van de lecture notes
[Show more]
Seller
Followmichouweimar
Reviews received
Content preview
Grade = 80% exam + 20% caseCase = 15% report + 5% presentation
Exam 4 open questions
Basic principles genetic improvement
Chapter 1: introduction
What is the best animal?
How do you breed animals so that their descendants will be better than today’s animals?
- This course
What is the best animal
Best = relative & subjective
Describe animal through traits
- Trait => any observable or measurable characteristic of an animal
- Observable trait = appearance
- Measurable trait = performance
- Trait = coat colour & weaning weight
P+G+E
- Phenotype => observed categories or measured levels for traits
- Phenotypes = red, 343kg
- Genotype => genetic background for its phenotype
- Environmental effects => effects that external factors have on animal’s performance
Importance of traits depends on: physical environment, management system & economic
factors
- Genotype determines degree to which animals are suited for their function in society
- Breeding objective => sensible goals for breeding programs
Selective breeding: past, present & future (L0)
Domestication selection
Pre domestication: natural selection
- Genetic adaptation of organism to environment
- Survival of the fittest: fitness determined by nature
Domestication => tame an animal, especially by generations of breeding
- Genetic adaptation of animals to new environment
- New env: captivity, food provided, protection
Artificial selection => human determines fitness
- Selective breeding
- Selection for confirmation
, - Exploiting genetic variation
Selective breeding theory
Mendelians vs biometricians
Fisher
- Infinitesimal model => traits are result of infinite #genes each with small effect
Selection index theory
Chapter 3
Optimal weighing of info from relatives & traits
I = b’ X
H = v’ A
Pb = Gv <-> b = P-1 Gv
Mixed model
Chapter 5
Addition to selection index theory
Adjusts for systematic environmental differences
Infinitesimal model
Most of the times: no clue about what genes affect trait
- Animal breeders practice genetics without genes
Genomics revolution
Make polymorphisms visible in lab
More cheap to genotype animal for SNPs
Still hard to detect which gene affects which trait
- Trait affected by many genes
Genomic selection
- Genomic selection can increase selection response still without knowing genes
What has been achieved?
Milk production NL
- Trend: +75kg milk/year
, - Selective breeding does not result in large & fast changes
- Effects of selective breeding are cumulative! makes breeding unique
Selection limits?
- There are limits, but we don’t know what they are
Correlated responses
- By selecting, other parts can also be unconsciously modified
- Fertility decreases when milk yield increases in cows
Balanced breeding
- Multiple trait selection (chapter 3)
- Economic values (chapter 4)
Selection in broilers
- Fast growth, less feed required
- Improved efficiency of food production
- Discussion on responsible breeding
Negative consequences of selective breeding can be avoided by balanced breeding
multiple trait selection
- Mistakes will still be made: we don’t know everything
- Mistakes due to wrong breeding goal
Recent developments
Global challenge regarding food security
- Increased demand for food
- Economics, environment & animal welfare
Additional phenotypes: traits to include in breeding goal
- Methane emission reduction
- Longevity
General problem genetic improvement
- Translate phenotypic observations into breeding values
- Select parents for next generation improvement maximised, while maintaining
genetic diversity
- Extension of breeding goal with new traits (environmental impact) novel tech
- Improve prediction of breeding values, inbreeding & phenotypes based on genomic
info
- Understanding relation between genotype & phenotype genome editing
Novel phenotyping technologies
- Sensors (camera, sound, GPS)
- Omics (protein content, antibodies)
- Organoids in vitro (feed efficiency, stress)
Genomic info & prediction
- Whole genome sequencing (lethal recessives, recombination)
- Gene expression
- DNA methylation
Genome editing
- Precise insertion, deletion, or replacement of DNA with molecular scissors
- CRISPR-CAS
, Chapter 2: response to selection (L1)
Part I
What are expected responses to selection of various plans?
Basic principles of genetic improvement
Understand different types of selection
Understand key components of response to selection
Breeding goal => specific traits with their desired direction of change over generations
Genetic model
Describe genetic quality
Phenotypic value = breeding value + environmental effect (+ µ)
Heritability => proportion of var(P) due to additive genetic effects
Other genetic models
- Repeated observations: repeatability (r)
Ep = permanent env effect
Et = temporary env effect
Repeated measurements model
- Multiple offspring: common env effects (c2)
Transmission model
Breeding value => prediction of genetic merit
- A≠G
- Gives an indication of performance of offspring
- Bull with A = +1000 kg milk daughters produce +500 kg more than average
Selection of parents = key to genetic improvement
Different types of selection
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller michouweimar. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.91. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
83662 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now