Ways to improve h2, r and consequently Genetic Gain

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Ways to improve h2, r and consequently Genetic
Gain
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Ways to improve h2,r and consequently Genetic Gain
P ? G E P ? A D I EP ET
VP VA VD VI VEP VET
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Ways to improve h2,r and consequently Genetic Gain
h2 Heritability is related to efficiency of
phenotypic selection on achieving genetic
gain. r Repeatability is related to culling
efficiency.
SPA- Standard Performance Analysis (Data
collection and analysis!!)
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Ways to improve h2,r and consequently Genetic Gain

• Environmental Uniformity Contemporary groups
• Accurate measurements Data Collection
• Environmental effects Adjustments for fixed
  effects

Goal is to reduce Ve and consequently reduce
Vp. For h2 it means increase proportion of Vp
that is additive For r it means increase
proportion of the Vp that is genetic
Environmental permanent
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Repeatability (rep)

• rep association between 2 or more records on
  same individual.
• Only applies to traits with repeatable records
  (e.g., milk yield, litter size, ewes wool
  production).

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• rep proportion of phenotypic variation due to
  genetics and all permanent effects (G EP).

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Repeatability (rep)

• Should an animal be culled after a first
  measurement / data record?
• What is the repeatability for that trait on the
  population?

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Ways to improve h2, r and consequently Genetic
Gain
Heritability (h2) proportion of the phenotypic
variance that is genetic or in other words,
Proportion of phenotypic variation on selected
animals that will be transmitted to the
offspring. Its a measure of ACCURACY when
performing phenotypic selection!!
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Ways to improve h2, r and consequently Genetic
Gain
Its a measure of ACCURACY when performing
phenotypic selection!! How to be more efficient
in selecting the genetically best animals using
the phenotypic information?
Alternative Population Situations
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Environmental Uniformity Contemporary groups

• Manage animals such that the environmental
  conditions are as similar as possible
• The Va remains unchanged, the Ve and consequently
  Vp are reduced. h2
• We are not making environmental conditions
  better, but making them more uniform

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Contemporary groups

• A group of individuals who experience a similar
  condition with respect a specific trait
• Same location
• Same age
• Same sex
• Adjusts for unequal environments and again
  increases h2 by reducing Ve and Vp

Phenotypic differences between animals on the
same contemporary group are due genetic
differences!!!
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Ways to improve h2,r and consequently Genetic Gain
Accurate Measurements The more accurate the
instruments used to take measurements, the higher
the h2 when compared to the same trait measured
with less precise instrumentsAgain consider h2
as a ratio of variances, h2Va/Vp-Va remais
unchanged-Ve and Vp are reducedPrecision has a
similar effect on h2 values
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Adjustment of Performance Records

• Use of Regressions to Adjust Performance Records
  (Standardization of records)
• Reduces bias due Environment
• - Increases h2 and thus Accuracy of Selection
• Contemporary Groups

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Adjustment of Performance Records

• Phenotypes are corrected for known fixed effects
• Fixed effects that can influence phenotype
  include
• -Sex
• -Born as single versus twin
• -Seasonal differences
• For fair comparison phenotypes are adjusted for
  these effects

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Adjustment of Performance Records
1-Express S as deviation from contemporary group
mean.
Example A 57 Kg male twin has S 57 55Kg 2Kg
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2- Adjust for effects separately only
applicable in absence of interaction between
effects
Example A 57 Kg male twin is advantaged by 5Kg
for being male and disadvantaged by 2.5Kg for
being a twin. Adjusted S 57-52.5 54.5Kg S (as
deviation from overall mean) 54.5 52.5 2Kg
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• Standardization of records

• Use of regressions to allow comparisons at same
  ages (days)

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• Standardization of records

• Use of regressions to allow comparisons at same
  ages (days)
• WW 205 days
• YW 365 days
• Carcass 480 days
• SC 365 days of age

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Adjustment of Performance Records
Adjustment Factors for Birth Weight. Values to be
added to the BW.
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Adjustment of Performance Records

• Adjusted weaning weight WW205
• WW205 (Actual wt. birth wt. / age at
  weighing) x 205 birth wt. age of dam factor

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Adjustment of Performance Records

• Example 1 A heifer calf weighed 74 lbs. at birth
  and 310 at weaning with the weaning age being 149
  days. The cow age is 2 years.

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Adjustment of Performance Records

• Example 1 A heifer calf weighed 74 lbs. at birth
  and 310 at weaning with the weaning age being 149
  days. The cow age is 2 years.

WW205
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Adjustment of Performance Records

• Example 1 A heifer calf weighed 74 lbs. at birth
  and 310 at weaning with the weaning age being 149
  days. The cow age is 2 years.

WW205
WW205
WW205 310 - 74 x 205 74 54 452.69 lbs
149
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Adjustment of Performance Records

• Example 2 A heifer calf weighed 65 lbs. at birth
  and 380 at weaning with the weaning age being 195
  days. The cow age is 4 years.

WW205
WW205
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Adjustment of Performance Records

• Example 2 A heifer calf weighed 65 lbs. at birth
  and 380 at weaning with the weaning age being 195
  days. The cow age is 4 years.

WW205
WW205 380 - 65 x 205 65 18 414.15 lbs
195
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Adjustment of Performance Records

• Measurement of Yearling Weight (365 days) In
  on-the-farm or ranch tests, the postweaning
  period should start on the date weaning weights
  are obtained (for example, actual weaning weight
  is used as initial weight on test). Because
  age-of-dam affects weaning weight, it is
  appropriate in on-farm tests to add postweaning
  gains in a 160-day, postweaning period to 205-day
  weaning weight, adjusted for age of dam to arrive
  at adjusted 365-day weight. The following
  formula is recommended

• Adjusted yearling weight YW365
• YW365 (A x 160) / No. of days between Wts.
  B
• A Actual Final Wt. - Actual Weaning Wt.
• B 205-day Weaning Wt. Adj. For Age-of-Da
• A x 160 postweaning gain

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Adjustment of Performance Records

• Example 3 A heifer calf weighed 82 lbs. at
  birth, 591 lbs at weaning with the weaning age
  being 210 days and 1036 lbs at 358 days of age.
  The cow age is 4 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?
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Adjustment of Performance Records

• Example 3 A calf (male) weighed 82 lbs. at
  birth, 591 lbs at weaning with the weaning age
  being 210 days and 1036 lbs at 358 days of age.
  The cow age is 4 years.

• WW205 (Actual wt. birth wt. / age at
  weighing) x 205 birth wt. age of dam factor

• WW205 (591 82 / 210) x 205 82 20 598.88
  lbs

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?
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Adjustment of Performance Records

• Example 3 A calf (male) weighed 82 lbs. at
  birth, 591 lbs at weaning with the weaning age
  being 210 days and 1036 lbs at 358 days of age.
  The cow age is 4 years.

• WW205 598.88 lbs

• YW365 A x 160 /No. of days between Wts. B
• A Actual Final Wt. - Actual Weaning Wt.
• B 205-day Weaning Wt. Adj. For Age-of-Da

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?
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Adjustment of Performance Records

• Example 3 A calf (male) weighed 82 lbs. at
  birth, 591 lbs at weaning with the weaning age
  being 210 days and 1036 lbs at 358 days of age.
  The cow age is 4 years.

• WW205 598.88 lbs

• YW365 (445 x 160 ) / 148 598.88) 1079.96
• A Actual Final Wt. - Actual Weaning Wt.
• B 205-day Weaning Wt. Adj. For Age-of-Da

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?
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Adjustment of Performance Records

• Example 3 A calf (male) weighed 82 lbs. at
  birth, 591 lbs at weaning with the weaning age
  being 210 days and 1036 lbs at 358 days of age.
  The cow age is 4 years.

• WW205 598.88 lbs

• YW365 1079.96 lbs

postweaning gain (in 160days) YW365 - WW205
481.08 lbs postweaning average daily gain (ADG)
postweaning gain / 160 3.01 lbs/day
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Adjustment of Performance Records

• Example 4 A heifer weighed 75 lbs. at birth, 435
  lbs at weaning with the weaning age being 190
  days and 916 lbs at 382 days of age. The age of
  the cow is 8 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?
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Adjustment of Performance Records

• 75 lbs. at birth,
• 435 lbs at weaning (age being 190 days)
• 916 lbs at 382 days of age
• The cow age is 8 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?

• WW205 (Actual wt. birth wt. / age at
  weighing) x 205 birth wt. age of dam factor

• WW205 (435 75 / 190) x 205 75 0 463.42
  lbs

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Adjustment of Performance Records

• 75 lbs. at birth,
• 435 lbs at weaning (age being 190 days)
• 916 lbs at 382 days of age
• The cow age is 8 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?

• WW205 463.42 lbs

• YW365 A x 160 /No. of days between Wts. B
• YW365 481 x 160 /192 463.42 76960/192
  463.42 864.25 lbs
• A Actual Final Wt. - Actual Weaning Wt.
• B 205-day Weaning Wt. Adj. For Age-of-Da

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Adjustment of Performance Records

• 75 lbs. at birth,
• 435 lbs at weaning (age being 190 days)
• 916 lbs at 382 days of age
• The cow age is 8 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?

• WW205 463.42 lbs

• YW365 864.25 lbs

postweaning gain (in 160days) YW365 - WW205
400.83 lbs postweaning average daily gain (ADG)
postweaning gain / 160 2.51 lbs/day
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Adjustment of Performance Records

• 75 lbs. at birth,
• 435 lbs at weaning (age being 190 days)
• 916 lbs at 382 days of age
• The cow age is 8 years.

What is the WW205, YW365, postweaning gain (in
160days) and postweaning average daily gain
(ADG)?

• WW205 463.42 lbs

• YW365 864.25 lbs

postweaning gain (in 160days) YW365 - WW205
400.83 lbs postweaning average daily gain (ADG)
postweaning gain / 160 2.51 lbs/day
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Contemporary Group

• Definition A group of animals that have
  experienced a similar environment with respect to
  the expression of a trait.
• Contemporaries typically perform in the same
  location, are the same sex, are of similar age,
  and have been managed alike.

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Contemporary Group

• P ? A D I EP ET
• P ? BV GCV Ecg Ep ET
• BV Breeding Value,
• GCV Gene Combination Value,
• CG Contemporary Group

- Animals on the same CG experienced similar
environment the differences between them will be
in a higher proportion due genetic and
consequently it will be easier to differentiate
animals with higher Breeding Value. - The
heritability and repeatability within CG will be
higher!!!
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Example of Contemporary Group

• Example 1
• Bull YW Herd Aver. P EBV
• h2 .4
• A 950 930 20 8
• B 930 880 50 20

Notice the differences in rank.
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Example of Contemporary Group

• Example 2
• Bull WW Herd Aver. P EBV
• h2 .4
• A 410 430
• B 520 480
• C 570 610
• D 410 450
• E 520 580
• F 570 510

What would be the rank for WW with and without
correcting for CG?
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Example of Contemporary Group

• Example 2
• Bull WW Herd Aver. P EBV
• h2 .4
• A 410 430 -20 -8
• B 520 480 50 20
• C 570 610 -40 -16
• D 410 450 -40 -16
• E 520 580 -60 -24
• F 570 510 60 24

Without FCgtBEgtAD
With FgtBgtAgtCDgtE
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Example of Contemporary Group

• Example 3
• Bull WW Herd Aver. P EBV
• h2 .4
• A 520 530
• B 620 590
• C 490 510
• D 510 450
• E 580 520
• F 620 620

Without
With
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Example of Contemporary Group

• Example 3
• Bull WW Herd Aver. P EBV
• h2 .4
• A 520 530 -10 -4
• B 620 590 30 12
• C 490 510 -20 -8
• D 510 450 60 24
• E 580 520 60 24
• F 620 620 0 0

Without FBgtEgtAgtDgtC
With DEgtBgtFgtAgtC