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Poultry Breeding Chapter 15
Poultry Breeding Chapter 15
43
Agriculture
Undergraduate 3
04/09/2018

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Term
A breeder has to decide...
Definition
1: which individuals would become parents of the next generation through artificial selection
2: how many offspring per parent would s/he generate
3: which females would be bred to which male.
Term
some mating strategies
Definition
-random mating
-assortive mating
Term
RANDOM MATING
Definition
A mating system in which mates are chosen at random and each male and female has an equal chance of mating.
Term
ASSORTATIVE MATING
Definition
The mating of either similar individuals (positive assortative mating, e.g. large individuals) or dissimilar individuals (negative assortative mating, e.g. large and small individuals).
Term
some combination strategies
Definition
-crossbreeding
-inbreeding
-line breeding
Term
Crossbreeding
Definition
Mating of sires of one breed, strain or line to dams of another breed, strain or line.
Term
Inbreeding
Definition
Mating of individuals related by ancestry.
Term
Line breeding
Definition
The mating of individuals to maintain a substantial degree of relationship to a highly productive ancestor(s) or group of ancestor(s).

-produces mild inbreeding
-example: sire may be mated to some of his daughters to produce more sons closely related to him than if he mated with other females
-sometimes considered as a useful insurance against loss of a sire from sudden death
Term
some consequences of inbreeding
Definition
1. Increases homozygosity and reduces heterozygosity. Inbreeding increases uniformity within a line or breed.
2. Expresses deleterious (lethal) recessive alleles with major effects
3. Reduced phenotypic performance.
Term
some deleterious (lethal) effects that can result from inbreeding
Definition
-twisted neck
-blindness
-etc.
Term
INBREEDING DEPRESSION
Definition
reduction in phenotypic value as a result of an increase in inbreeding level.
Term
the genetic basis of inbreeding depression
Definition
dominance
Term
what decreased heterozygosity does to phenotype
Definition
reduces the contribution of dominance variation to the phenotype
Term
In general, Inbreeding tends to reduce...
Definition
FITNESS
Term
Relationship between inbreeding and fertility in broiler breeders
Definition
inversely related

greater inbreeding means less fertility
Term
opposite of inbreeding depression
Definition
"hybrid vigor" or heterosis
Term
“HYBRID VIGOR” or HETEROSIS
Definition
Change in performance of offspring or progeny population over that of the parental populations
Term
Hybrid vigor or heterosis results from...
Definition
1: increased heterozygosity
2: Masking of expression of unfavorable recessive alleles
Term
Fitness Traits
Definition
Traits that relate to an animal’s ability to survive and reproduce.
Term
how to calculate heterosis
Definition
Heterosis = ((Average of crosses - Average of Parents) / (Average of Parents)) x 100%
Term
OUTBREEDING
Definition
Mating of unrelated individuals
Term
Why outbreeding?
Definition
1. To utilize heterosis
2. To take advantage of breed, strain or line complementarity.
Term
genetic basis of heterosis
Definition
dominance
Term
common procedure to estimate heterosis in practice
Definition
diallele cross
Term
diallele cross
Definition
basically crossing of lines, strains or breeds
Term
example of a diallele cross
Definition
[image]

this is for 3 strains
Term
General Heterosis or General Combining Ability (GCA)
Definition
GCA = (((crossbred average) - (parental average)) / (parental average)) * 100
Term
Specific Combining Ability (SCA)
Definition
Heterosis between lines or strains
Term
how to calculate specific combining ability (SCA)
Definition
example:

SCA = ((((AB + BA) / 2) - ((AA + BB) / 2)) / ((AA + BB) / 2)) * 100
Term
"nicking"
Definition
The fact that some lines combine well together
Term
some mating systems that cause inbreeding, but cause no heterosis
Definition
-Self fertilization (plants)
-Full-sib mating/parent-offspring
-Half-sib mating
-First Cousins
Term
mating system that causes no inbreeding, but also no heterosis
Definition
random mating
Term
some mating systems that cause no inbreeding, but cause heterosis
Definition
-Outbreeding
-Crossbreeding
-Species crosses
Term
details of outbreeding
Definition
- within a breed
- strain or line crossing
Term
details of crossbreeding
Definition
- breeds within a species
Term
potential problems of species crosses
Definition
-fertility problems
-chromosome incompatibility
Term
Crossbreeding is designed to take advantage of...
Definition
heterosis
Term
In poultry, lines are crossed to...
Definition
compliment each other
Term
2 reasons lines are crossed
Definition
-partly to utilize heterosis to improve reproduction
-partly to combine the different characteristics for which the lines were previously selected
Term
reproductive traits that can be improved by crossing lines
Definition
-fertility
-hatchability
-viability
Term
recurrent selection
Definition
A highly inbred line of animals that is nearly homozygous in all desirable alleles is used as a test population. Males of this inbred line are usually mated to females of a “new” line

[image]
Term
Reciprocal Recurrent Selection
Definition
Instead of using a test line for mating, two lines are mated

[image]
Term
rotational crosses
Definition
[image]
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