Transcript GPVEC Module IV Cundiff - University of Nebraska–Lincoln

Applied Beef Cattle Breeding and Selection
Inbreeding and Heterosis in Beef Cattle
Larry V. Cundiff
ARS-USDA-U.S. Meat Animal Research Center
2008 Beef Cattle Production Management Series-Module IV
Great Plains Veterinary Education Center
University of Nebraska, Clay Center
August 1, 2008
Homework
Participants
Module 2
Module 3
Davidson
X
X
Fox
X
Frese
X
Furman
X
X
Jones
X
X
Linhart
X
X
Matlick
X
X
Van Boening
X
X
X
X
Anderson
Castleberry
Langon
Werhman
Ondrack
Email homework to
[email protected]
Degrees of inbreeding according to relationship of mates
(Lush, 1945)
Species
Outbreeding
within a
breed
Full
sib
Self
Fertilization
crosses
First
cousin
Half
sib
Random
Cross
Mating
In a pure breeding
breed
Zygotic Frequency with Self Fertilzation
of a Heterozygote (Aa)
Female
Male gamete
gamete
.5 A
.5 a
.5 A
.25 AA
.25 Aa
.5 a
.25 Aa
.25 aa
Change in genotypic frequency with
self fertilization
Generation
0
1
2
3
4
5
…
Various
but many
AA
Aa
100
25
50
37.5
25
43.75
12.5
46.875
6.25
48.4375
3.125
…
…
50
0
aa
25
37.5
43.75
46.875
43.75
…
50
Effects of different degrees of
dominance on phenotypic value
1
0.8
0.6
AA
Aa
aa
0.4
0.2
0
-0.2
No
Dominance
(additive)
Partial
dominance
Complete
dominance
Effects of inbreeding on heterozygosity/homozygosity
(Cundiff and Gregory, 1977)
H
E 100
T
?
E
80
R
O
Z
60
Y
G
O
40
S
I
T
20
Y
(%)
0
Aa
HomoZygous
line
0
?
20
40
60
80
100
Pure
Sire
Inbred
Daughter Breed
Line
Random
Or
F = .5
mated
Full sib
Cross
breeding
H
O
M
O
Z
Y
G
O
S
I
T
Y
(%)
AA
Or
aa
Average expected performance of crossbred,
purebred, and inbred lines with additive and
non additive gene effects.
Frequency (%) per /genotype
AA
Crossbred
Purebred
Sire-daughter
Inbred line F=.5
Homozygous line
0
10
20
30
50
Aa
100
80
60
40
0
aa
0
10
20
30
50
Additive
0.5
0.5
0.5
0.5
0.5
Partal
Dom.
0.75
0.70
0.65
0.60
0.50
Complete
Dom.
1.0
0.9
0.8
0.7
0.50
Effects of inbreeding in cattle
(Brinks et al., 1975. Western Regional Project W-1, Tech. Bulletin 123)
• Fertility (percentage of cows pregnant declined
2% and 1.3% with each 10% increase in inbreeding
of the dam and calf, respectively.
• Percentage calf crop weaned declined 1.6% and
1.1% with each 10 percent inbreeding of the dam
and calf, respectively.
• Inbreeding also depressed growth and maternal
weaning weight.
Estimating Heterosis for a specific two breed cross
Sire breed
Dam breed
Calf breed
Weaning wt
H
A
HA
430
A
H
AH
416
A
A
AA
405
H
H
HH
395
HA = 430 = .5gH + .5 gA + hIha + mA
AH = 416 = .5gH + .5 gA + hIha + mH
AA = 405 =
HH = 395 =
gA +
gH +
+ mA
+ mH
(.5)(HA + AH) + .5 (AA + HH) = 423 – 400 = 23 = hIah
Estimating Maternal Heterosis
C X A = .5gC + .5 gA + hIca + mA
C X B = .5gC + .5 gB + hICB + mB
C X AB = .5gC + .25 gA + .25gB + .5hIAC + .5hIBC + .5mA +
.5 mB + hMAB
C X BA = .5gC + .25 gB + .25gA + .5hIAC + .5hIBC + .5mA +
.5 mB + hMAB
.5[( C X AB) + (C X BA)] – .5[(C X A) + (C X B)] = hMAB
HETEROSIS EFFECTS IN CROSSES OF BOS TAURUS X BOS TAURUS
BREEDS AND IN CROSSES OF BOS INDICUS X BOS TAURUS BREEDS
FROM DIALLEL CROSSING EXPERIMENTS
Trait
No.
Est.
Bos taurus X
Bos taurus
Units
%
Bos indicus X
No.
Bos taurus
Est. Units %
Crossbred calves (individual heterosis)
Calving rate, %
Survival to weaning, %
Birth weight, kg
Weaning weight, kg
Postweaning ADG, g/d
Yearling weight, kg
Cutability, %
Quality grade, 1/3 gr.
11
16
16
16
19
27
24
24
3.2
1.4
.8
7.3
34
13.2
-.3
.12
4.4
1.9
2.4
3.9
2.6
3.8
-.6
---
4
10
6
6
3.3 11.1
21.7 12.6
116 16.2
.3
---
HETEROSIS EFFECTS IN CROSSES OF BOS TAURUS X BOS TAURUS
BREEDS AND IN CROSSES OF BOS INDICUS X BOS TAURUS BREEDS
FROM DIALLEL CROSSING EXPERIMENTS
Trait
Bos taurus X
Bos taurus
Units
%
No.
Est.
Bos indicus X
No.
Bos taurus
Est. Units
%
Crossbred cows (maternal heterosis)
Calving rate, %
Survival to weaning
Birth weight, kg
Weaning weight, kg
Longevity, yrs
Lifetime prod.
No. Calves
Cum. wn. wt., kg
13
13
13
13
3
3.5
.8
.7
8.2
1.36
3.7
1.5
1.8
3.9
16.2
3
3
.97
17.0
25.3
272
7
7
6
12
9.9
4.7
1.9
31.1
13.4
5.1
5.8
16.0
Heterosis
Weight of Calf Weaned Per Cow
Exposed To Breeding
23.3
•More than half of this effect
is dependent on use of
crossbred cows.
14.8
Percent
•Heterosis increases
production per cow 20 to 25%
in Bos taurus x Bos taurus
crosses and at least 50% in
Bos indicus x Bos taurus
crosses in subtropical
regions.
8.5
Straightbred Straightbred
cows
cows
straightbred
X-bred
calves
calves
8.5
X-bred
cows
X-bred
calves
LONGEVITY AND LIFETIME PRODUCTION OF
STRAIGHTBRED HEREFORD (H), ANGUS (A), HEREFORD X
ANGUS (HA) AND ANGUS X HEREFORD (AH) COWS
Trait
Longevity, yrs.
Lifetime production
No. calves
Wt of calves weaned, lb.
*P < .05
H
8.4
Breed group
A
HA AH Heterosis
9.4
11.0 10.6
1.9*
5.9 6.6
7.6 7.6
2405 2837 3259 3515
1.3*
766*
Conclusions
• Heterosis Effects are greatest for lowly heritable traits:
Reproduction
Survival
Longevity
• Heterosis effects are moderate for moderately
heritable traits:
Direct and maternal weaning weight
Postweaning gain
• Heterosis effects are small for highly heritable traits:
Feed efficiency
Carcass traits
Retail product %
Fat thickness
Marbling
Static Three-breed Cross System
A
B
C
A
A
AB
25%
of
Cows

 25-30%  45-50%
of
Cows

Offspring marketed
Pounds of calf/cow
increased about19%
of
Cows


Rotational Crossbreeding
Systems
Heterosis for Production Per Cow in Hereford,
Angus, and Shorthorn Rotational Crosses
Two breed
rotation
Three breed
rotation
Observed (%)
Expected (%)a
First Generation
16
24
19
23
Observed (%)
Expected (%)a
Second Generation
24
35
14
21
aBased
on individual and maternal heterosis observed
in F1 generation and assumes that retained heterosis
is proportional to retained heterozygosity.
Genetic Composition and Heterosis Expected
in a Two-Breed Rotation
Generation
1
2
3
4
5
6
7
aBased
Additive genetic
comp. of progeny
Sire
A
B
breed
%
%
A
B
A
B
A
B
A
50
25
63
31
66
33
67
50
75
37
69
34
67
33
Heteroz. of
progeny
relative to F1
Est.
in wt.
wnd/cowa
%
%
100
50
75
63
69
66
67
8.5
19.0
13.8
16.4
15.2
15.8
15.5
on heterosis effects of 8.5% for individual traits and 14.8% for
maternal traits, when loss of heterosis in proportional to loss of
heterozygosity
Genetic Composition and Heterosis Expected in a
Three-Breed Rotation
Sire
Generation breed
Additive Genetic
Heteroz. of Est. increase
Comp. of Progeny progeny
in wt.
A
B
C relative to F1 wnd/cowa
%
%
%
%
%
1
2
3
4
5
6
7
8
50
25
12
56
28
14
57
29
aBased
A
B
C
A
B
C
A
B
0
50
25
12
56
28
14
57
50
25
62
31
16
58
29
14
100
100
75
88
88
84
86
86
8.5
23.3
21.2
18.6
20.5
20.2
19.7
20.0
on heterosis effects of 8.5% for individual traits and 14.8% for maternal
traits when loss of heterosis is prportional to loss of heterozygosity.
Rotational Crossbreeding
Systems
Rotational crossing systems
maintain heterosis
proportional to heterozygosity
Next time : Composite Populations
and alternative crossbreeding systems.
MARC I
¼ Limousin, ¼ Charolais,
¼ Brown Swiss,
c Angus and c Hereford
Angus
MARC II
¼ Simmental, ¼ Gelbvieh,
¼ Hereford and ¼ Angus
MARC III
¼ Pinzgauer, ¼ Red Poll,
¼ Hereford and ¼ Angus
Limousin
Simmental
Pinzgauer
Charolais
Gelbvieh
Red Poll
Brown Swiss
(Braunvieh)
Hereford
Hereford
Angus
Angus
Hereford
HETEROSIS EFFECTS AND RETAINED HETEROSIS
IN COMPOSITE POPULATIONS VERSUS CONTRIBUTING
PUREBREDS (Gregory et al., 1992)
Trait
Birth wt., lb
200 d wn. wt., lb
365 d wt., females, lb
365 d wt., males, lb
Age at puberty, females, d
Scrotal circumference, in
200 d weaning wt., (mat.), lb
Calf crop born, (mat.), %
Calf crop wnd., (mat.), %
200 d wn. wt./cow exp. (mat.), lb
Composites minus purebreds
F1
F2
F3&4
3.6
42.4
57.3
63.5
-21
.51
33
5.4
6.3
55
5.0
33.4
51.4
58.6
-18
.35
36
1.7
2.1
37
5.1
33.7
52.0
59.8
-17
.43
Composite populations
maintain heterosis
proportional to heterozygosity
(n-1)/n or 1 – S Pi2
Rotational crossing systems
or
composite populations
maintain significant heterosis
MODEL FOR HETEROZYGOSITY IN
A TWO BREED COMPOSITE
Breed
Dam
Breed of sire
½A
½B
½A
½B
¼ AA
¼ BA
(n-1)/n or 1 – S Pi2 = .50
¼ AB
¼ BB
MODEL FOR HETEROZYGOSITY IN
A THREE BREED COMPOSITE
Breed
Dam
.50 A
.25 B
.25 C
Breed of sire
.50 A
.25 B
.25 AA
.125 BA
.125 AC
.125 BA
.0625 BB
.125 BC
1 – S Pi2 = (1 - .375) = .625
.25 C
.125 CA
.0625 CB
.0625 CC
Weaning Wt Marketed Per Cow Exposed for Alternative
Crossbreeding Systems Relative to Straightbreeding (%)
System
Hi
(+ 8.5%)
Hm
(+14.8%)
Wean. wt
marketed
per cow exp
0
Straight breeding
0
0
2-breed rotation (A,B)
3-breed rotation (A,B,C)
4-breed rotation (A,B,C,D)
.67
.86
.93
.67
.86
.93
15.5
20.0
21.7
2-breed composite (5/8 A, 3/8 B)
2-breed composite (.5 A, .5 B)
3-breed composite (.5A, .25 B, .25C)
4 breed composite (.25A,.25B,.25C,.25D)
.47
.5
.625
.75
.47
.5
.625
.75
11.0
11.7
14.6
17.5
F1 bull rotation (3-breed: AB, AC)
F1 bull rotation (4-breed: AB, CD)
.67
.83
.67
.83
15.5
19.3
Composite populations provide for
effective use of
• Heterosis
• Breed differences
• Uniformity and end product
consistency
Genetic Variation in Alternative Mating Systems
Optimum
Assumes that the Two F1’s Used are of Similar Genetic Merit
Genetic potential for USDA
Quality Grade and USDA
Yield Grade is more
precisely optimized in cattle
with 50:50 ratios of
Continental to British breed
inheritance.
COMPLEMENTARITY
is maximized in terminal crossing systems
Cow Herd
Small to moderate size
Adapted to climate
Optimal milk production
for feed resources
Terminal Sire Breed
Rapid and efficient growth
Optimizes carcass composition
and meat quality in
slaughter progeny
Progeny
Maximize high quality lean beef
produced per unit feed consumed
by progeny and cow herd
Rotational and Terminal Sire
Crossbreeding Programs
Cow
Age
2 Breed Rotation

No.
A
1
2
3
20
18
15
45%
4
5
12
13
12
1
55%
Lbs. Calf/Cow
B
Two Breed
Composite
1/2A - 1/2B

T x (A-B)
21%
T x (A-B)
18%
Weaning Wt Marketed Per Cow Exposed for Alternative
Crossbreeding Systems Relative to Straightbreeding (%)
System
Hi
+ 8.5%
Hm
+14.8%
Straight breeding
0
0
2-breed rotation (A,B)
3-breed rotation (A,B,C)
4-breed rotation (A,B,C,D)
.67
.86
.93
2-breed composite (5/8 A, 3/8 B)
2-breed composite or F1 bulls (.5 A, .5 B)
3-breed composite (.5A, .25 B, .25C)
4 breed composite (.25A,.25B,.25C,.25D)
F1 bull rotation (3-breed: AB, AC)
F1 bull rotation (4-breed: AB, CD)
Wean. wt
Terminal
marketed
crossa
per cow exp (+5% wt/calf)
0
0
.67
.86
.93
15.5
20.0
21.7
20.8
24.1
25.4
.47
.5
.625
.75
.47
.5
.625
.75
11.0
11.7
14.6
17.5
17.3
17.8
20.3
22.2
.67
.83
.67
.83
15.5
19.3
20.8
23.6
a Assumes 66 % of calves marketed (steers and heifers) are by terminal sire breed
out of more mature age dams and 33% are by maternal breeds (steers only).
SUMMARY
Figure 6. Use of heterosis, additive breed effects and
Complementarity with alternative crossbreeding systems.
Implications for Crossbreeding
•
Similarity in mean performance of British and Continental European
breeds means they are more suited for use in rotational crossbreeding systems today than 30 years ago
•
Performance levels are not expected to fluctuate as much with
rotational crossing for growth traits and cow size . Growth rate can
be stabilized by using Across-breed EPDs.
•
Differences in birth weight are still significant and warrant use of
sire breeds with lighter birth weight on first calf heifers (i.e., Angus,
Red Angus, etc.).
•
Intergeneration fluctuations in milk production still persist but they
are less than half as great as 30 years ago. Milk levels can be
stabilized by using Across-breed EPDs.
Implications for Crossbreeding
•
Advantages of terminal sire crossing systems are not as great
today as 30 years ago due to similarity of breeds for rate and
efficiency of growth.
• However, differences between British and Continental breeds in
carcass traits are still significant and relatively large.
• Inter generation fluctuations in mean performance for carcass
traits are still large and significant.
• For carcass traits, uniformity and end-product consistency can
still be enhanced by use of composite populations or hybrid bulls.
•
Adaptation to intermediate subtropical/temperate environments
can be optimized with greater precision by use of composite
populations or hybrid bulls.
Heterosis proportional to heterozygosity in various matings
Mating type
Progeny
Dam
Pure breed
0
Two breed F1 cross (A x B)
100
F2 (AB x AB)
50
F3 (AB x AB) (or F4, ..Fn) = 2 breed Composite
50
Backcross (A x AB)
50
1st backcross interse (A-AB x A-AB)
37.5
¾-1/4 composite (.75A, .25B)
37.5
5/8-3/8 composite (.625 A, .375 B)
47
2 breed rotation
67
0
0
100
50
100
50
37.5
47
67
Three way cross (A x BC)
100
1st 3-way interse (A - BC) x (A-BC)
62.5
3 –breed composite (.5 A, .25 B, .25C)
62.5
3 breed rotation (A, B, C)
86
Rotation F1 hybrids, 1 common breed (AB -AC) 67
100
100
62.5
86
67
Four way cross
4- breed composite (.25 A, .25B, .25C, .25 D)
4-breed rotation (A, B, C, D)
Rotation 2 F1 hybrids (AB - CD)
100
75
93
83
100
75
93
83
Rotational and Terminal Sire
Crossbreeding Programs
Cow
Age
2 Breed Rotation
3 Breed Rotation

No.
A
1
2
3
20
18
15
45%
4
5
12
13
12
1
55%

B

A
Lbs. Calf/Cow
T x (A-B)
21%
B


C
T x (A-B-C)
24%
BREED DIFFERENCES
an important genetic resource
Cross breeding of composite populations can be used to
exploit:
•
HETEROSIS
•
COMPLEMENTARITY among breeds optimize
performance levels for important traits and to match
genetic potential with:
Market preferences
Feed resources
Climatic environment
Composite populations provide for
effective use of
• Heterosis
• Breed differences
• Uniformity and end product
consistency
CEFFICIENTS OF VARIATION IN PUREBRED AND
COMPOSITE POPULATIONS (Gregory et al., 1992)
Trait
Gestation length, d
Birth wt.
200 d wn. wt.
365 d wt., females
365 d wt., males
Age at puberty (females)
Scrotal circumference
5 yr cow wt, lb
5 yr height, in
Steer carcass wt, lb
Rib-eye area
Retail product, %
Retail product, lb
Purebreds
.01
.11
.09
.08
.09
.08
.07
.07
.02
.08
.10
.04
.19
Composites
.01
.12
.09
.08
.09
.07
.07
.08
.02
.08
.10
.06
.20
COMPLEMENTARITY
is maximized in terminal crossing systems
Cow Herd
Small to moderate size
Adapted to climate
Optimal milk production
for feed resources
Terminal Sire Breed
Rapid and efficient growth
Optimizes carcass composition
and meat quality in
slaughter progeny
Progeny
Maximize high quality lean beef
produced per unit feed consumed
by progeny and cow herd
General Considerations
• Rotational Systems
Provide for more effective use of
• Heterosis
• Composite populations
Provide for more effective use of
• Breed differences
• Uniformity and end product consistency
Composite populations provide for
effective use of
• Heterosis
• Breed differences
• Uniformity and end product
consistency
Percentage Cows Remaining
Effect of Heterosis on Percentage Cows Remaining in Herd
At Different Ages Relative to Those Originally Retained
as Breeding Heifers
Crossbred cows
Straightbred cows
Age At Exposure to Breeding (years)
Rotational Crossbreeding Programs
2 Breed
3 Breed


A
B

A
B


C
Increase Lbs. Calf
Per Cow 15%
Increase Lbs. Calf
Per Cow 19%
Genetic Variation in Alternative Mating Systems
Optimum
Assumes that the Two F1’s Used are of Similar Genetic Merit
Weaning Wt Marketed Per Cow Exposed for Alternative
Crossbreeding Systems Relative to Straightbreeding (%)
System
Hi
+ 8.5%
Hm
+14.8%
Straight breeding
0
0
2-breed rotation (A,B)
3-breed rotation (A,B,C)
4-breed rotation (A,B,C,D)
.67
.86
.93
2-breed composite (5/8 A, 3/8 B)
2-breed composite or F1 bulls (.5 A, .5 B)
3-breed composite (.5A, .25 B, .25C)
4 breed composite (.25A,.25B,.25C,.25D)
F1 bull rotation (3-breed: AB, AC)
F1 bull rotation (4-breed: AB, CD)
Wean. wt
Terminal
marketed
crossa
per cow exp (+5% wt/calf)
0
0
.67
.86
.93
15.5
20.0
21.7
20.8
24.1
25.4
.47
.5
.625
.75
.47
.5
.625
.75
11.0
11.7
14.6
17.5
17.3
17.8
20.3
22.2
.67
.83
.67
.83
15.5
19.3
20.8
23.6
a Assumes 66 % of calves marketed (steers and heifers) are by terminal sire breed
out of more mature age dams and 33% are by maternal breeds (steers only).