Lecture 4: Introduction To Genetic Selection In Poultry Flashcards
What is the origin of genetics?
Mendelian inheritance
What is Mendelian inheritance?
- single gene with two alleles
- dominant: masks the expression with only one copy
- recessive: require two copies to be expressed
- homozygous: two copies of either dominant or recessive
- heterozygous: one dominant and one recessive allele
What is the issue with Mendelian inheritance?
- traits are controlled by more than 1 gene, not as simple
What is co-dominance?
No recessive genotype, appearance of both parental phenotypes shows in the offspring
What is incomplete dominance?
Dominant allele does not completely mask the effects of the recessive allele. Blend of both alleles (black and white makes grey)
Difference between bird genetics and mammals
- female sex chromosomes: ZW (heterozygous)
- male sex chromosomes: ZZ (homozygous)
- can sex the chicks through feather growths - Z chromosome carries feather growth
What is single-trait selection?
Make progress on trait rapidly, may not be beneficial in the long run, least adapted to the environment
What is multiple-trait selection?
More traits, slower progress, but bird is more adapted to environmental factors
Environment includes…?
Housing and nutrition
Where is genetic potential never fully achieved?
In commercial settings (at farm level)
What is a thermal neutral zone?
Ideal temperature, part of the barn where the bird doesn’t have to use energy to adjust body temperature - optimum performance zone
Environment is very important for..
Genetic expression in poultry
What is heritability
The proportion of variability within a population that can be attributed to inherited genetic factors as opposed to environmental ones. Heritability is estimated for all measure phenotypes to assess their usefulness for selection
Low vs high heritability?
Low heritability - low transmission to the next generation
High heritability - high transmission to the next generation
What is the range of heritability?
0 to 1 (0% to 100%)
Outline of a generic breeding program
- Definition of production system
- Definition of breeding goal
- Collection of information - phenotypes, genotypes
- Determining selection criteria - breeding value est.
- Selection and mating
- Dissemination
- Evaluation
What was the question in divergent breeding?
How to select for a male bird when trying to breed for egg production? Ad vice versa
Divergent breeding
Layers (selected for egg) vs broiler (selected for meat)
What is progeny testing?
A test that tests the value for selective breeding of a genotype by looking at the progeny produced by different matings
What is the broiler breeder paradox?
If the broiler characteristic in a line improve, its reproductive capacity will be impaired
What is causing welfare concerns in the broiler breeder paradox?
Controlled growth of pullets by feed restriction to improve reproductive capacity leads to welfare concerns
What is the elephant in the room?
Inbreeding
What are the benefits of inbreeding?
Higher rates of homozygosity - good for specific traits
What are the cons of inbreeding?
- reduced survival and fertility of offspring
- major issues for pure and pedigree lines
