Breeding

The desires of the producer and the traits necessary for animals production in a certain field

What is the “best” animal?

Through careful selective breeding and standardization of enviroment

How do you breed animals so their descendants will be better than the previous?

Systems approach

Taking into consideration the environment and the type of product the animal will be producing in order of effectively and efficiently breed

Continuous

Traits show (blank) variation

Economic

Most (blank) traits are controlled by hundreds of genes

Bell shaped

Variation in genes have a (blank) curve

Quantitative

Objectively measured, involves numbers and measurements

Qualitative

Descriptive and subjective, can differ from person to person, environment plays little role

1-4 qualitative

(blank) pairs of genes control one trait in (blank) traits

Many pairs

Quantitative traits have (blank) of genes affecting them; usually of economic importance

Pleiotropy

Genes that have an effect on more than on trait

P=G+E

How to calculate phenotype

P=phenotype

G=genotype

E=environment

Contemporary group

A group of animals that have something in common

Herd

Sex

Breed

etc.

Ratio= (Individual measurement/Average measurement of group) x 100

Compare animals for a trait within a contemporary group.

False

Environmental differences do not make animals different

Environmental differences

Nutrition

Health

Weather

Injury

Management

Fertility

Time of mating during heat

Birth season

Known differences

Differences in an animals environment that are known and factored in

Unknown differences

Differences in an animal environment that are unknown and cannot be factored in accordingly

Adjusted data

Data that utilizes differing environmental factors into statistical livestock data

205-day WW= ((actual WW - birth weight)/weaning age in days) x 205) + birth wt

Weaning weight adjustment

Transmitting ability

The likelihood of an animal to transmit certain genes to their offspring

Expected Progeny Differences (EPD)

A prediction of future offspring performance relative to some standard

Cannot be compared across breeds

Progeny

Offspring

Using statistical procedures and large amounts of information

How are EPD’s calculated

Individual records

Ancestors and offspring records

Heritability of trait

Genetic correlation of trait with other traits

What data is used in calculating EPD’s

Correlation

The tendency for genes to affect each other and or multiple traits

Heritability (H^2)

How well a physical trait is passed on to further generations

< .20

Heritability of reproductive traits, low

.2-.4

Heritability of growth traits, moderate

> .4

Heritability of carcass traits, high

higher

The (blank) h^2 is the better the response that trait has to selection

Correlated responses

Change seen in traits that were not directly selected for; positive or negative

Higher wean weight; higher birth weights

(blank) is often associated with (blank)

False

EPD’s predict performance of an individual animal (T/F)

Genetic worth

EPD’s are the best predictor of (blank)

Calfs own genes-inherent ability to grow- EPD weaning weight

EPD weaning weight

EPD wwt

Reflects expected weaning weight performance of a bull’s calves

Genes of the calf’s dam – nutritional \n environment, i.e., milk - EPD milk

EPD milk production

EPD MILK

reflects that portion of expected \n weaning weight performance of a bull’s \n daughters’ calves influenced by her \n milking ability

Birth weight

Calving ease

Weaning weight

Yearling weight

Yearling height

Scrotal circumference

Direct Production EPD’s

Milk

Total maturity

Mature daughter weight

Mature daughter height

Calving ease

Stayability

Maternal production EPD’s

Carcass weight

Marbling

Ribeye area

Backfat

% retail product

Carcass EPD’s

1

As accuracy approaches (blank) EPD is more reliable

Amount of information

Number of progeny

Heritability and genetic correlations

What affects accuracy

Better management

Litter size in hogs is best improved through what?

You can select for environmental differences and carry it into the next generation (T/F)

False

To genetically improve populations

What is the purpose of breeding

Selection and Mating

What are the two tools in breeding

Selection

Which animals will be the parents, how long they stay breeding

Mating

Which male is bred to which female

Gene frequency

The object of selection is to change (blank)

Genetic variation

Having a uniform group of animals to limit the number of misfits in the group, produce consistent data

Accuracy

How well we can predict the genotype from the phenotype

Genetic variation (or differences)/genetic variation + environmental variation

h^2=

Environmental variation

Reducing (blank) will make the genetic portion of p=G+E greater (h^2 will be greater)

Greater intensity

(blank) results in faster genetic progress because the selection differential is greater

Selection differential

The superiority of the individuals to be mated as compared to the herd average; aka. reach

cull

(blank) the animals that are below average for the trait you want

Males

(blank) have a greater selection differential

more lower

The (blank) traits in a selection program the (lower) the selection differential is for each respective trait

Generation Interval

The average age of the parents when offspring are born

avg. age of parents/2

Formula for genetic interval

% intramuscular fat

Ribeye area

Fat

Ultrasound EPD’s

Increased

(blank) number of progeny give more accurate EPD’s

Genetically improve populations

What is the purpose of breeding

Selection

Which animals will be the parents and how long will they remain in the breeding population

Mating

Which male is bred to which female

Change gene frequency

What is the object of selection

Gene frequency

How rare of abundant a particular gene is in a population

Max genetic variation

Accuracy

Intensity of selection

Generation interval

Factors that affect rate of genetic improvement

uniform

Livestock producers and breeders prefer livestock that is (blank)

Accuracy

How well we can predict the genotype from the phenotype

Standardizing

(blank) the environment makes selection more accurate

Intensity of selection

Proportion needed for herd replacements

Smaller the fraction the greater the intensity (greater genetic progress)

Selection differential (SD)/reach

The practice of culling the least productive animals and breeding the most productive

Males

Selection intensity is greater for (blank)

Smaller fraction saved=greater intensity

Males sire several offspring a year

Why is selection emphasis greater on males

Number of traits being selected for

What affects reach

Pedigree

Record of animals ancestry

closer

The (blank) in pedigree a relative is the more valuable it is to evaluation

Performance test

Evaluation of an animal on the basis of its own record

Progeny test

Evaluation of an animal based on the performance of its offspring, highly accurate but takes time and requires large numbers

Tandem method

System of multiple trait selection

Select single correlated traits

Select for milk production milk fat % falls

Independent culling methods

Establish minimum cull standards and select simultaneously but independently for each character

Most prevalent method of selection

Cull anything below standards

Individuals may be culled due to lack of one trait yet have excellence in other areas

Selection Index

Formula where all important traits are combined into one overall value, 100 is avg.

Individuals are calculated for net genetic worth

requires good records

Producers cannot determine own index due to complexity

Traits that are: heritable, easy to measure, and associated with economic value

Accurate genetic predictions

Availability of genetic variation

Basis for development of breed and utilization of performance records

Effective selection requires…

Inbreeding

Mating of animals that are more closely related than the average of the breed population they originated from

Increases homozygous genes (reduces genetic variation)

Increased breed purity

Test for undesirable recessive genes

Overall performance is decreased

Consequences of inbreeding

Fix specific traits or develop a new breed

Get heterosis when crossing inbred lines

Eliminate undesirable genes

Why inbreed

Linebreeding

Mild form of inbreeding that attempts to concentrate the inheritance of one or more outstanding ancestors in a pedigree

Outbreeding

Mating of individuals that are not related

Increases heterozygosity

Destroys family lines

Consequences of outbreeding

Species cross

Form of outbreeding between closely related species

Ex. Horse and donkey

Outcrossing

Form of outbreeding of individuals of the same species

Safest form

Grading up

Form of outbreeding that has a continuous use of purebred sires of the same breed in a herd or flock

Widely used in cattle herds without crossbreeding

Crossbreeding

Form of outbreeding where individuals of differing breeds mate

Normally results in heterosis

Breed complementation

Strengths and weaknesses of breeds used to complement each other

True

Traits with high heritability have low heterosis, but traits with low heritability have high heterosis (T/F)

greater heterosis

The (blank) the species differences the greater the (blank)

Rotational cross

Crossbred female that is bred to a male of a third breed or is bred back to teh breed of sire that is present in her genetic makeup in the lowest percentage