Animal breeding terminology

Question 1

Trait

Answer 1

Any observable or measurable characteristic of an individual.
For example
Observable trait - coat colour Measurable trait – lactation yield

Question 2

Qualitative traits

Answer 2

– A trait in which phenotypes are expressed in categories (“Either/Or”)
– Are affected by one or at most a very few genes
– Examples
• Polled vs. horned condition
• Coat color in Angus (black vs. red)
• Coat color in Shorthorns (red, roan, or white)
– A trait in which phenotypes show
continuous (numerical) expression
– Polygenic control - many genes, each having a relatively small contribution to the genetic merit of the animal.
– e.g. height, weight, milk production, backfat thickness, etc.
– Exception - A major gene

Question 3

Phenotype

Answer 3

– Is the appearance or observed performance for a trait in an animal.
– An animal has a phenotype for coat color (e.g., black vs. red).
– An animal has a phenotype for weight
– A dairy cow has a phenotype for milk production

Question 4

Genotype

Answer 4

– Is the animal’s genetic makeup.
– A genotype is the combination of genes at a single locus or at a number of loci.
– For example, an Angus cow or bull has a genotype for coat color (BB, Bb, or bb).
– An animal also has a genotype for weight, milk production, etc, which consists of all the genes that influence that particular trait.

Question 5

What is the Dominant phenotype for Angus cow

Answer 5

Black(BB,Bb), red (bb) are recessive

Question 6

Simply-inherited Trait

Answer 6

– A trait only affected by a few genes e.g. horned/polled

Question 7

Polygenic Trait

Answer 7

A trait affected by many
genes, no single gene having an overriding influence e.g. weaning weight in sheep, fertility in mammals, conformation and personality in dogs, and growth rate in cattle.

Question 8

Germ Plasm

Answer 8

The genetic material in the form of live animals, semen, or embryos.

Question 9

Seedstock

Answer 9

Breeding stock, animals whose role is to be a parent to contribute genes to next generation

Question 10

Purebred

Answer 10

Wholly of one breed or line

Question 11

Population

Answer 11

A group of intermating animals. The

term may refer to a breed, a herd or an entire species

Question 12

Line

Answer 12

A group of related animals with in a breed.

Question 13

Breeding Value

Answer 13

The value of an animal as a (genetic) parent.

Question 14

Heritability

Answer 14

A measure of the

strength of the relationship between breeding values and phenotypic values for a trait in a population.

Question 15

Genetic Prediction

Answer 15

Area of animal breeding

concerned with measurement of data, statistical procedures, and computational techniques for predicting breeding

Question 16

Sire Summary

Answer 16

A list of genetic predictions,

accuracy values and other useful information about sires in a breed.

Question 17

Progeny data

Answer 17

Information on the genotype or performance of descendants of an individual

Question 18

Major Gene

Answer 18

• A gene that has a major influence on a quantitative trait
• Quantitative traits, while mostly influenced by many genes, each having a small effect, in some cases are also influenced by major genes

Question 19

Double muscling gene

Answer 19

– Cattle with this gene are extremely heavily muscled.
– Double muscling is due to a mutation in the myostatin or growth and differentiation factor (GDF-8) gene
– Mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition
– Penotype occurs at a high frequency in some breeds of cattle
• Belgian Blue and Peidmontese.

Question 20

Callipyge gene

Answer 20

– A gene found in sheep that results in a condition similar to double muscling in cattle.
– “Callipyge” comes from the Greek words for “beautiful buttocks”.
– Sheep with this gene have extreme muscling in their loins and hind legs.
• The gene greatly increases muscling and decreases fat.

Question 21

Halothane gene (stress gene)

Answer 21

– Called so because of the adverse effect of halothane anaesthetic on pigs carrying this gene
– Found primarily in the Pietran breed and Pietran crossbreds with a low frequency in most breeds
– Causes reduced litter size, reduced growth rate, and reduced carcass length
– Also causes increased loin eye area and increased lean%
– Biggest disadvantage is that it causes PSE
• Pigs with this gene are susceptible to stress and tend to have PSE (pale, soft, exudative) pork.

Question 22

Rendement Napole (RN-) Gene

Answer 22

• Appears to be dominant
• Found primarily in purebred or crossbred Hampshire populations – “Hampshire effect” or “Acid meat”
• Negative effects on meat pH, water holding capacity, color, drip loss, cooking loss, and processing yield

Question 23

Variation of Quantitative Characters

Answer 23

• Variation is defined as the observable difference between individuals
• We want to identify sources of variation in animals and separate the variation into its component parts

Question 24

What can Phenotypic variation can be separated into

Answer 24

– Genetic causes

– Environmental causes

Question 25

What can Genetic causes of variation be subdivided into

Answer 25

– Additive components

– Non additive components

Question 26

What does non additive gene caused by

Answer 26

interactions among genes
– Dominance is due to interactions between alleles at the same locus
– Epistasis is due to interactions between genes at different loci

Question 27

• Environmental causes of variation

Answer 27

– Diet
– Weather
– Health program
– Facilities
– Management practices

Question 28

Hereditary Causes of Variation

Answer 28

• Differences in genotypes of individuals cause genotypic variation, which in turn causes phenotypic variation
• Genotype of an individual is fixed at conception and stays the same until death
• Genotype of an individual is determined by the parents
– One-half of the genes come from each parent
• No two individuals have the same genotype (unless identical twins or clones)

Question 29

Are Qualitative traits influenced by environment

Answer 29

No

Question 30

Are Quantitative traits influenced by environment

Answer 30

Yes
– Even for a highly heritable trait, a large amount of the phenotypic variation is due to the environment
– h2 of post-weaning gain in cattle = 0.55 or 55%
• 45% of the variation in post-weaning gain is due to the environment, even though post-weaning gain is a highly heritable trait

Question 31

Booroola (FecB) Merino gene

Answer 31

– Found in a strain of Merino sheep
– Booroola = mutation in BMP1B receptor gene
– (bone morphogenic protein receptor gene
– oocyte & ovary granulosa cells)
– Lack of signal to limit ovulation to one follicle
– This gene increases the ovulation rate and number of lambs born in sheep.
• Average number of lambs born per ewe lambing = 2.4 (range = 1 to 6 lambs)
• Litter size in heterozygous ewes is increased by about 0.9 lambs.

Question 32

Double muscling gene

Answer 32

– Cattle with this gene are extremely heavily muscled.
– Double muscling is due to a mutation in the myostatin or growth and differentiation factor (GDF-8) gene
– Mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition
– Penotype occurs at a high frequency in some breeds of cattle
• Belgian Blue and Peidmontese.

Question 33

Callipyge gene

Answer 33

– A gene found in sheep that results in a condition similar to double muscling in cattle.
– “Callipyge” comes from the Greek words for “beautiful
buttocks”.
– Sheep with this gene have extreme muscling in their
loins and hind legs.
• The gene greatly increases muscling and decreases fat.

Question 34

Halothane gene (stress gene)

Answer 34

– Called so because of the adverse effect of halothane
anaesthetic on pigs carrying this gene
– Found primarily in the Pietran breed and Pietran crossbreds with a low frequency in most
breeds
– Causes reduced litter size, reduced growth rate, and reduced carcass length
– Also causes increased loin eye area and increased lean%
– Biggest disadvantage is that it causes PSE
• Pigs with this gene are susceptible to stress and tend to have PSE (pale, soft, exudative) pork.

Question 35

Rendement Napole (RN-) Gene

Answer 35

• Appears to be dominant
• Found primarily in purebred or crossbred Hampshire
populations – “Hampshire effect” or “Acid meat”
• Negative effects on meat pH, water holding capacity,
color, drip loss, cooking loss, and processing yield

Question 36

Permanent Environmental Effects

Answer 36

Are environmental effects that stay the same from one record to the next on an animal
– Stay with animal throughout its lifetime
– If a cow loses function of one quarter of her udder due to injury, it will influence her milk production in all future lactations
• The feeding program used to raise heifers, if extreme
(e.g., too much feed or not enough feed) can influence
mammary gland development, which becomes a
permanent environmental effect
– Will influence all future lactations

Question 37

Temporary Environmental Effects

Answer 37

• Are environmental effects that change from one record to the next on an animal
– Cold and snowy winter one year vs. mild winter the next year
– Drought one summer vs. normal rainfall the next summer