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Animal Breeding > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What is the new equation for phenotype?

A

P = BV + D + I + Ep + Et
D=dominance effect
I=epistatic effect

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2
Q

What kind of estimate is heritability?

A

Population

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3
Q

What is heritability?

A

Relationship of the difference in animal performance due to inheritance

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4
Q

How does heritability vary?

A

Population to population and environment to environment

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5
Q

What are the 2 types of heritability?

A 
Broad sense (H^2)
Narrow sense (h^2)
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6
Q

What is broad sense heritability?

A

Measure of the strength of the relationship between performance and genotypic value for a trait in a population

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7
Q

How is broad sense heritability denoted?

A 
H^2 = r^2p,g 
r^2p,g = correlation between p and g
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8
Q

What is broad sense heritability used in?

A

Identical individuals

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9
Q

What is narrow sense heritability?

A

Measure of the strength of the relationship between performance and breeding values for a trait in a population

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10
Q

Hos is narrow sense heritability denoted?

A 
h^2 = r^2p,bv
r^2p,bv = correlation between p and BV
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11
Q

What is narrow sense heritability used in?

A

Animal production

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12
Q

What does broad sense include?

A

BV plus GCV or dominance and epistatic effects

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13
Q

What does narrow sense include?

A

BV

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14
Q

Why is GCV not included in narrow sense?

A

GCV cannot be inherited

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15
Q

What is the range of narrow sense heritability?

A

0 to 1

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16
Q

What are the ranges for low, moderate, and high heritability?

A

Less than 0.2 is low heritability
0.2-0.4 is moderate heritability
More than 0.4 is high heritability

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17
Q

What is parental performance when there is high h^2?

A

A good indicator of offspring performance

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18
Q

What does parental performance do when there is low h^2?

A

Reveals little about offspring performance

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19
Q

What are examples of trait estimates for fitness?

A

Fertility and survivability

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20
Q

What is heritability like for fitness?

A

Low h^2

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21
Q

What are examples of trait estimates for production?

A

Milk production and growth rate

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22
Q

What is heritability like for production?

A

Moderate h^2

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23
Q

What are examples of trait estimates for terminal?

A

Carcass
Skeletal
Mature weights

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24
Q

What is heritability like for terminal?

A

High h^2

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25
Q

What is the alternative definition for narrow sense?

A

h^2 = Va / Vp = Va / (Va + Vd + Vi + Vep + Vet)

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26
Q

When there is a high environmental effect, what is heritability like?

A

Low

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27
Q

When there is a low environmental effect, what is heritability like?

A

High

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28
Q

What is the objective for heritability and selection?

A

To choose an individual with the best breeding value

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29
Q

In phenotypic selection, what does performance reveal when there is low heritability?

A

Little about breeding value

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30
Q

What is genetic change like in phenotypic selection with low heritability?

A

Slow

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31
Q

In phenotypic selection, what does performance reveal when there is high heritability?

A

It is a good indicator about breeding value

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32
Q

What is genetic change like in phenotypic selection with high heritability?

A

Fast

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33
Q

What is heritability used in the prediction of?

A

BV
PD
PA

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34
Q

What does heritability and predictions indicate?

A

How conservative a prediction should be

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35
Q

What traits do producers tend to select?

A

More highly heritable traits that can make significant change

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36
Q

What do large differences in performance lead to?

A

Large differences in BVs

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37
Q

What do producers choose not to change low heritable traits through?

A

Management

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38
Q

What kind of estimate is repeatability?

A

Population

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39
Q

How does repeatability vary?

A

From population to population and environment to environment

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40
Q

What is repeatability a measure of?

A

The strength of the relationship between repeated records for a trait in a population

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41
Q

What is repeatability denoted as?

A

r = r_p1,p2

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42
Q

What is the range of repeatability?

A

-1 to 1

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43
Q

What are the ranges for low, moderate, and high repeatability?

A

Less than 0.2 is low repeatability
0.2-0.4 is moderate repeatability
More than 0.4 is high repeatability

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44
Q

If repeatability is high, what is the the first record used as?

A

A good indicator for the 2nd record

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45
Q

If repeatability is low, what is the the first record for the 2nd record?

A

A poor indicator of the 2nd record

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46
Q

What traits are used for repeatability?

A

Traits that have more than one performance record

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47
Q

What is the alternate definition for repeatability?

A

r = (Va + Vd + Vi + Vep) / (Va + Vd + Vi + Vep + Vet)

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48
Q

What is repeatability like when there is a low temporary environmental effect?

A

High

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49
Q

What is repeatability like when there is a high temporary environmental effect?

A

Low

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50
Q

For culling purposes, what should you do when there is high repeatability?

A

Cull poor producing animals

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51
Q

For culling purposes, what should you do when there is low repeatability?

A

Get more records before making a decision

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52
Q

What does repeatability become when predicting producing abilities?

A

Adjustment factor

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53
Q

What are 3 ways to improve heritability and repeatability?

A

Environment uniformity
Accurate measurement
Contemporary groups

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54
Q

What do you want in environment uniformity?

A

Environment the same for different animals

Not making the environment better, just similar

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55
Q

When using accurate measurements, what do you adjust for?

A

Known environmental effects

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56
Q

What are some known environmental effects?

A 
Age of dam
Age of animal
Sex of animal
Parity
Milkings per day
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57
Q

What are contemporary groups?

A

Groups of animals that have experienced a similar environment with respect to the expression of a trait

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58
Q

How do you compare contemporary groups?

A

As a deviation from the group mean

p – p_cg

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59
Q

How many animals do you want in a contemporary group?

A

5 or more

60
Q

What is the new model for P with contemporary group?

A

P = μ + BV + GCV + Ecg + E

61
Q

What is the equation with contemporary group for BV and PA?

A

P – Pcg = BV + GCV + Ep + Et

P – Pcg = PA + GCV + Ep + Et

62
Q

What is a trait ratio?

A

Ratio of an individual’s performance to the average performance of all individuals in the contemporary group

63
Q

How do you calculate the ratio?

A

(Pi / Pcg) x 100

64
Q

What are the 4 factors of genetic change?

A

Accuracy of selection
Selection intensity
Genetic variation
Generation interval

65
Q

What is the symbol for the rate of genetic change or response to selection?

A

ΔBV/t

66
Q

What is the symbol for accuracy of selection?

A

r_bv, bv(hat)

67
Q

What does selection intensity measure?

A

How “choosy” breeders are in selecting individuals

68
Q

If there is a high intensity, what does the at say about selecting animals?

A

Selecting very best animals

69
Q

If there is no intensity, what does the at say about selecting animals?

A

Selecting animals at random

70
Q

What is the symbol for selection intensity?

A

i

71
Q

How do you calculate selection intensity?

A

(SCs – SC) / σsc

72
Q

What is the rate of genetic change like when accuracy and intensity are low?

A

Slow

73
Q

What is the rate of genetic change like when accuracy and intensity are high?

A

Fast

74
Q

What is genetic variation?

A

Variability of BV within a population for a trait

75
Q

What is the symbol for genetic variation?

A

σ_BV

76
Q

What is generation interval?

A

Amount of time required to replace one generation with the next

77
Q

In closed populations, what is generation interval defined as?

A

The average age of parents when their offspring are born

78
Q

What is the symbol for generation interval?

A

L

79
Q

What is the equation for genetic change?

A

(r_bv, bv(hat) x i x σ_BV) / L

80
Q

What is the equation for genetic change with phenotypic selection?

A

(h^2 x i x σ_p) / L

81
Q

What is the equation for genetic change when there is a male and female involved?

A

(h^2 x (im + if) x σ_p) / (Lm + Lf)

82
Q

If L decreases, what happens to other factors?

A

They decrease

83
Q

If accuracy increases, what happens to intensity?

A

It decreases (and vice versa)

84
Q

If you test fewer males, is there more or less to select from? What does having fewer males mean for females?

A

There’s less to select from

More females, more records

85
Q

If you test more males, is there more or less to select from? What does having more males mean for females?

A

More to select from

Less females, less records

86
Q

When there are fewer males, what happens to intensity and accuracy?

A

i decreases and acc increases

87
Q

When there are more males, what happens to intensity and accuracy?

A

i increases and acc decreases

88
Q

What is replacement rate?

A

Rate at which newly selected individuals replace existing parents in a population

89
Q

If intensity increases, what happens to generation interval?

A

It increases (and vice versa)

90
Q

What is the normal rule for females?

A

i increases, L increases

91
Q

What is the rule used when deciding if females should be saved?

A

If sires are genetically far superior to dams, there are many replacement females
If sires are slightly better, there are fewer replacements and you can be more selective

92
Q

What is selection risk?

A

Risk that the true breeding values of replacements will be significantly poorer than expected

93
Q

What is selection risk like for males?

A

Fewer sires, more intensity, more risk

94
Q

What is selection risk like for females?

A

Not an issue

95
Q

Why is the selection of males more important than females?

A

More progeny
Higher accuracies
Up to 90% of genetic change can be attributed

96
Q

What does the rate of genetic change depend on?

A

Accuracy of selection or accuracy of BV predictions

97
Q

What is the accuracy of selection increased by?

A 
Increasing h^2
Managing animals uniformly 
Taking careful measurements
Adjusting for known environment
Use of contemporary groups
98
Q

How do you increase accuracy of selection further?

A

Use as much info as possible

Weigh each piece of info appropriately

99
Q

What is selection index a method of?

A

Genetic prediction

100
Q

What is the equation for selection index?

A

I = b_n x x_n

101
Q

What are 3 sources that information used in calculating genetic prediction for an individual comes from?

A

Individual’s own performance
Performance records of ancestors
Performance record of descendants

102
Q

What data is used in selection index?

A

Individual’s own performance for trait
Individual’s paternal half sib average performance for a trait
Individual’s average progeny performance for a trait
Performance of individual, half sib, and progeny for correlated trait

103
Q

How is phenotypic info usually expressed?

A

As a deviation from contemporary group mean

104
Q

Why should old contemporary groups not be used?

A

Because of updates

105
Q

What is the equation for a prediction using a single source of information?

A

I = bx

106
Q

What is common among half sibs?

A

Paternal environment

107
Q

What is common among full sibs?

A

Maternal environment

108
Q

What are 3 factors affecting accuracy of prediction?

A

h^2
Pedigree relationship
# of records

109
Q

What are half sib records a good indicator of?

A

Sire

110
Q

What do half sib records not determine?

A

BV of progeny

111
Q

How do you calculate a prediction for multiple sources of information?

A

I = b1x1 + b2x2 + b3x3…..

112
Q

What are pedigree estimates?

A

Prediction based solely on pedigree data

113
Q

What is BLUP?

A

Best linear unbiased prediction

114
Q

What does BLUP calculate?

A

Solutions simultaneously of a number of equations for an entire population of animals

115
Q

Why is BLUP a preferred method?

A

Large scale evaluation
Typically entire breeds
Field data taken by producers

116
Q

What are the types of statistical models in BLUP?

A

Sire
Maternal grandsire
Animal models

117
Q

What are animal models?

A

Most popular

Evaluates all animals instead of certain ones

118
Q

What does BLUP account for? (6)

A

Differences in the mean breeding values of contemporary groups
Genetic trends
Info from all individuals in population
Non-random mating
Culling due to performance
Direct and maternal components of a trait

119
Q

What are direct components of a trait?

A

Effect of an individual’s genes on the performance

120
Q

What are maternal components of a trait?

A

Environment provided by the dam

121
Q

What are maternal components affected by?

A

Genes of the dam

122
Q

What can BLUP predict?

A 
EBV's
EPD's
MPPA's
Total maternal value
BLUE
Any animal in population
123
Q

What is BLUE?

A

Best linear unbiased estimators

124
Q

What is an example of BLUE?

A

Sex effects
Management
Environment

125
Q

What is done before BLUP in large populations?

A

Central tests

126
Q

What are central tests?

A

Comparing animal from different herds or flocks

127
Q

What are factors of central tests?

A

Only a few traits
Animal performance only
Location preference

128
Q

When was BLUP first used?

A

1980s

129
Q

What did early information from BLUP do?

A

Designed tests

130
Q

What does BLUP do now?

A

Field data reported to breed associations or other agencies for evaluation

131
Q

Why is it called a sire summary?

A

Because males have more progeny

132
Q

What are direct components’ performance attributed to?

A

Genes inherited from the sire

133
Q

What is total maternal?

A

Combination of direct and maternal

134
Q

What are accuracy values a measure of?

A

The relationship between trait values and their prediction

135
Q

What is the range of accuracy values?

A

0 to 1

136
Q

If you expand the pool of available sires, what happens to selection intensity?

A

Increases

137
Q

If Bull A’s EPD is +10 for weaning weight and bull B’s EPD is -5 for weaning weight, what do you expect for the progeny?

A

We expect Bull A’s progeny to weigh 15 pounds heavier on average than Bull B’s progeny at weaning when mated to similar females

138
Q

What does an EPD of zero represent?

A

The breed average for the trait in a specific year

139
Q

When there is high accuracy, how much selection risk is there?

A

Little

140
Q

When there is low accuracy, how much selection risk is there?

A

High

141
Q

What does accuracy tell about?

A

Reliability of EPD

142
Q

What are some faulty data examples on pedigrees?

A

Parental misidentification

143
Q

What are some faulty data examples on performance records?

A

Falsifying records

Incomplete reporting

144
Q

What are some faulty data examples on adjustment?

A

Wrong information about known environmental effects

145
Q

What are some faulty data examples on contemporary groups?

A

Reported as members of the wrong group

Treatment differences

146
Q

What are some faulty data examples on relationship among groups?

A

Individuals related in different groups

AI increases connectedness

147
Q

What are some faulty data examples on G x E interactions?

A

Significant interaction can cause problems

Low heritability traits are more susceptible

Animal Breeding (4 decks)

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