Lecture 4: Introduction To Genetic Selection In Poultry

Question 1

What is the origin of genetics?

Answer 1

Mendelian inheritance

Question 2

What is Mendelian inheritance?

Answer 2

• 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

Question 3

What is the issue with Mendelian inheritance?

Answer 3

• traits are controlled by more than 1 gene, not as simple

Question 4

What is co-dominance?

Answer 4

No recessive genotype, appearance of both parental phenotypes shows in the offspring

Question 5

What is incomplete dominance?

Answer 5

Dominant allele does not completely mask the effects of the recessive allele. Blend of both alleles (black and white makes grey)

Question 6

Difference between bird genetics and mammals

Answer 6

• female sex chromosomes: ZW (heterozygous)
• male sex chromosomes: ZZ (homozygous)
• can sex the chicks through feather growths - Z chromosome carries feather growth

Question 7

What is single-trait selection?

Answer 7

Make progress on trait rapidly, may not be beneficial in the long run, least adapted to the environment

Question 8

What is multiple-trait selection?

Answer 8

More traits, slower progress, but bird is more adapted to environmental factors

Question 9

Environment includes…?

Answer 9

Housing and nutrition

Question 10

Where is genetic potential never fully achieved?

Answer 10

In commercial settings (at farm level)

Question 11

What is a thermal neutral zone?

Answer 11

Ideal temperature, part of the barn where the bird doesn’t have to use energy to adjust body temperature - optimum performance zone

Question 12

Environment is very important for..

Answer 12

Genetic expression in poultry

Question 13

What is heritability

Answer 13

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

Question 14

Low vs high heritability?

Answer 14

Low heritability - low transmission to the next generation
High heritability - high transmission to the next generation

Question 15

What is the range of heritability?

Answer 15

0 to 1 (0% to 100%)

Question 16

Outline of a generic breeding program

Answer 16

1. Definition of production system
2. Definition of breeding goal
3. Collection of information - phenotypes, genotypes
4. Determining selection criteria - breeding value est.
5. Selection and mating
6. Dissemination
7. Evaluation

Question 17

What was the question in divergent breeding?

Answer 17

How to select for a male bird when trying to breed for egg production? Ad vice versa

Question 18

Divergent breeding

Answer 18

Layers (selected for egg) vs broiler (selected for meat)

Question 19

What is progeny testing?

Answer 19

A test that tests the value for selective breeding of a genotype by looking at the progeny produced by different matings

Question 20

What is the broiler breeder paradox?

Answer 20

If the broiler characteristic in a line improve, its reproductive capacity will be impaired

Question 21

What is causing welfare concerns in the broiler breeder paradox?

Answer 21

Controlled growth of pullets by feed restriction to improve reproductive capacity leads to welfare concerns

Question 22

What is the elephant in the room?

Answer 22

Inbreeding

Question 23

What are the benefits of inbreeding?

Answer 23

Higher rates of homozygosity - good for specific traits

Question 24

What are the cons of inbreeding?

Answer 24

• reduced survival and fertility of offspring
• major issues for pure and pedigree lines

Question 25

How to avoid inbreeding?

Answer 25

Four way cross breeding