Selection and Breeding

Structure of primary broiler breeder stocks has how many pedigree pure line birds at the top?

0.4 million pedigree birds from 35 to 40 pure lines

Structure of primary broiler breeder stocks has how many end product meat birds at bottom?

400,000

Sire Lines (male lines)

broiler lines selected primarily for performance of males

• males from crosses of these lines used as fathers to produce production offspring

Dam lines (female lines)

broiler lines selected primarily for performance of females

• females from the crosses of theses lines sold as mothers to produce production offspring

What stock can be sold?

grand parent, parental, commercial product (EP)

• bottom three in chart

What stock cannot be sold?

pedigree foundation, great grand parents

Grand parents will sell

female and male but only one from each like

• male 1, female 2, male 3, female 4

Parental stock will sell

only male lines 1 and 2, female lines 3 and 4

Commercial stock will sell

male and female

Primary broiler breeder company structure is shaped like a

pyramid

How many purelines?

35-40 purelines

Purelines undergo

genetic selection for improvement in major economic traits

Male lines improve

growth rate, edible meat yield, feed conversion

Female lines improve

egg production, but also have good growth rate and repro traits

Genetic improvement made in pedigree lines is passed down thorugh

multiplication process

How long does multiplication process take?

4 years, and genetic improvement is diluted since selection is minimized or does not exist

• genetic comp in an individual changes during meiosis

Some steps of multiplication can be skipped if

populations are large enough

Broilers of pedigree pure lines will serve as

great grand parents to produce grand parents

In reproduction of pure lines and great grandparents what mating technique is used?

artificial insemination

Grandparents are crossed to grandparents from other lines to

generate parent stocks that are commercially available

What stocks are actual broilers used in broiler prod?

offspring of parent stock (EP or commercial stock)

The efficiency of energy retention in broilers peaks when?

Early in life

Does efficiency of energy retention continuously go up throughout a broiler’s lifetime?

No, it will decrease over time

• constant for first 1/3 of growth period

What are the two main components of metabolizable energy in broilers?

Heat production and energy retained

Heritability for reproductive traits is high or low?

low

What is performed regularly to identify superior crosses?

test crosses

Which term describes the deviation observed between reciprocal crosses?

Reciprocal effect

What is the heritability estimate for egg production typically considered to be?

Low (<0.3)

Is reciprocal recurrent selection is more applicable to broiler or layer selection?

Layer selection

Which of the following traits is typically negatively correlated with egg production?

Body weight

What is an advantage of line crosses and pyramidal structure?

they take advantage of heterosis (hybrid vigor)

Growth associated traits are:

• live body weight

• body weight gain

• growth rate (g/day)

• meat comp and yield

• feed consumption and efficiency

• fat content

Energy retain is mostly for

protein and fat

Growth requires that metabolizable energy is larger or smaller than heat production?

larger

What happens to the ratio of protein to fat as animals mature?

It decreases

• animals have more energy go to protein when young

Is more energy required to grow lean meat or fat?

Fat

Is genetic effect sex-linked?

Partially sex-linked

Is genetic effect polygenic (influenced by multiple genes)?

Yes

What is the growth curve?

an accelerating growth phase, decelerating growth phase, limiting mature weight

Does heterosis in growth exist?

Yes

Does growth respond to genetic selection?

Yes. Heritability ranges from 0.3-0.7

Agemax is

the age when maximum rate of weight gain is reached

Broiler body weight and weight gain are pos or neg correlated w/feed consumption?

positively

Broiler body weight and weight gain are pos or neg correlated w/feed conversion?

negatively

Live body weight is pos or neg correlated w/abdominal fat?

positively

Weight gain is pos or neg correlated w/abdominal fat?

negatively

Do faster or slower growers show better conformation of carcass?

Faster growers

Do fast or slow growing broilers have higher mortality rate?

Fast growing

Indoor vs Outdoor living affecting protein distribution is an env or genetic effect?

environmental

Fast vs slow growing chickens relates to env or genetic effects?

Genetic

Selection for growth traits is one or multiple stages?

multiple

What kinds of selection is used for growth traits?

Mass selection and index selection

Age of first egg refers to

when layers reach sexual maturity and are able to lay eggs

Heritability for egg production is additive or non additive genetic effect?

non-additive genetic effect

Is viability a factor for survivor egg prod measurement?

no

Within line selection is used to

maintain and select several pure lines and use pure lines for three and four way cross to produce high performance offspring for prod purposes

Line cross is used to

select parents that produce higher heterosis that results from epistasis and dominant effect (non additive genetic effect)

Reciprocal recurrent selection is a form of family selection based on what effect?

Reciprocal effect

• the lines that serves better as females are called dam/female line, line serves better as males called sire/male lines

Reciprocal effect is the

deviation between line crosses of two parental lines in which their roles as female or male parents are reversed

The purpose of the reciprocal effect approach is to

select parents that prod higher heterosis, which is considered more in layers than broilers