Bell Ranch: Integrated Seedstock and Commercial Programs

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Bell Ranch Integrated Seedstock and Commercial
Programs
Genetics
Mule Camp produces 40 bulls each year for the
commercial enterprise.
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Weaning
Selection is for the weaning weight of the calves
? 205 days of age
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Question
If we select for weaning weight and increase the
growth potential of our cattle What will happen
to the mature size of our cow herd?
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Animal Science Introductory Courses Quail Project
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Project
Selection for 6 week weight. 3 lines High
growth, Low growth, Control 5 generations of
selection
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Selection
Selection was based on the individuals own
performance. h2 of 6 week weight about 50 The
accuracy of the selection criteria is 0.70
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(No Transcript)
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Lecture 23
Correlated Response
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Question What happens to other traits when
selection is for one trait?
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Question What happens to other traits when
selection is for one trait?
?y
?x
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Question What happens to other traits when
selection is for one trait?
?y
Selection Differential for Y
?x
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Correlated Response
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Correlated Response

• change in one trait resulting from selection on
  another trait

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Correlated Response

• change in one trait resulting from selection on
  another trait
• response can often be undesirable
• example turkeys

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Correlated Response

• change in one trait resulting from selection on
  another trait
• response can often be undesirable
• example turkeys
• response is based on genetic covariance between
  traits
• ?BVx,BVy

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Correlated Response Why does a genetic covariance
exist?
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Correlated Response Why does a genetic covariance
exist? 1) Pleotrophy -- one gene influences
more than one trait (permanent)
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Correlated Response Why does a genetic covariance
exist? 1) Pleotrophy -- one gene influences
more than one trait (permanent) 2) Link
age -- genes influencing two traits
physically linked (temporary)
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Correlations
Positive verses negative correlations
Beneficial verses antagonists correlations
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Correlated Response
bBVy on BVx ?BVy,BVx ?2BVx
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Correlated Response
bBVy on BVx ?BVy,BVx ?2BVx
change in BVy per unit change in BVx
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Correlated Response
bBVy on BVx ?BVy,BVx ?2BVx
change in BVy per unit change in BVx CRy
bBVy on BVx ? G (per generation) bBVy
on BVx ? g (per year)
x
x
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Revisit the Quail Project
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Correlated Response
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What is my dogs name?
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Superior
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Huron
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Ontario
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Dog Rowdy
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Selection versus Mating Systems
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Selection
Objective change gene frequency
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Selection
Objective change gene frequency -- Change in
frequencies for quantitative traits is slow. --
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Genetic Merit
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Genetic Merit value of individual genes
(selection)
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Genetic Merit value of individual genes
(selection) value of gene pairs (mating
systems)
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Genetic Merit value of individual genes
(selection) value of gene pairs (mating
systems) value of combination across loci
(mating system)
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Mating Systems
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Mating Systems

• Planned matings of selected parents

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Mating Systems

• Planned matings of selected parents
• Objective optimize gene combinations

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Mating Systems

• Planned matings of selected parents
• Objective optimize gene combinations
• Three Example Systems
• Inbreeding
• Line breeding
• Cross breeding

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Inbreeding -- the systematic mating of related
animals
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Inbreeding -- the systematic mating of related
animals generation Full Sibs A B C D
0
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Inbreeding -- the systematic mating of related
animals generation Full Sibs A B C D
0 E F 1
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Inbreeding -- the systematic mating of related
animals generation Full Sibs A B C D
0 E F 1 G H 2
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Inbreeding Each generation animals become more
related to each other, hence each generation the
inbreeding coefficient becomes larger.
Remember that the inbreeding coefficient is ½ the
relationship of the parents.
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Inbreeding Fx Generation Selfing F.S. H.S.
0 0 0 0
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Inbreeding Fx Generation Selfing F.S. H.S.
0 0 0 0 1 .5 .25 .125
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Inbreeding Fx Generation Selfing F.S. H.S.
0 0 0 0 1 .5 .25 .125 2
.75 .38 .220
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Inbreeding Fx Generation Selfing F.S. H.S.
0 0 0 0 1 .5 .25 .125 2
.75 .38 .220 5 .97 .67 .450
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Inbreeding With a line, animals become more
similar (uniformity), because gametes of any
individual become more similar.
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Inbreeding With a line, animals become more
similar (uniformity), because gametes of any
individual become more similar. Line 1 2 3 ?
? ? F.S. F.S. F.S.
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Inbreeding Between lines individuals become more
dissimilar (homozygous at different loci for
different alleles). Line 1 ? 2 ? 3 ? ? ? F
.S. F.S. F.S.
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• Inbreeding
• Using the inbreeding coefficient at generation t,
  we can estimate
• Within line variation, ?2BVW(t)
• Between line, ?2BVB(t)
• Total genetic variation, ?2BVT(t)

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Inbreeding ?2BV0 BV variance at
generation zero Ft inbreeding
coefficient at generation t
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Inbreeding ?2BV0 BV variance at
generation zero Ft inbreeding
coefficient at generation t After t
generations ?2BVW(t) (1 - Ft) ?2BV0
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Inbreeding ?2BVB(t) 2Ft ?2BV0 and ?2BVT(t
) ?2BVW(t) ?2BVB(t) (1 - Ft) ?2BV0
2Ft?2BV0 (1 Ft) ?2BV0
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Remaining Schedule
Four lectures left QTL discovery in dogs
(Raluca) Mating systems line breeding and
crossbreeding (Raluca) Heterosis Captive Animal
Breeding Programs
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