Chapter 6: Understanding Genetics for Use in Goat Production

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Understanding Genetics
For Use In
Goat Production
Dr. Dennis Onks
Director
Middle TN Research Center
University of Tennessee
PHENOTYPE
AN ANIMAL’S VISUAL EXPRESSION OR
PERFORMANCE IN ANY TRAIT
The Phenotype is the outcome of
Genetic Transfer as developed
in a production Environment
PHENOTYPE
Defined as the sum of the genetic
and environmental variation
The Genetic variation accounts for 25% of
The Phenotype while the Environment
Accounts for 75%!
Sound Breeding Program
Maximum Genetic Improvement occurs
In a Herd Environment that allows the
Improved Genetics to be Expressed
Sources of
Environmental Variation
1. Weather
2. Land Topography
3. Structural Resources
4. Forages and Feeding
5. Health and Sanitation
Genetic Variation is the study of
How Traits are Inherited
•All body cells contain “Blueprints” with
instructions as to how an animal will look or
act etc.
•DNA or Deoxyribonucleic Acid contains the
genes of traits in the double helix ribbons
located in every cell
GENE
The combination of genes are attached to
chromosomes which guide the animal to express
A trait or response
http://library.thinkquest.org
Species differ in chromosomes
Humans
23 pairs of chromosomes
Cattle
30 pairs of chromosomes
Sheep
27 pairs of chromosomes
Swine
19 pairs of chromosomes
Chicken
39 pairs of chromosomes
Goat
30 pairs of chromosomes
Horse
16 pairs of chromosomes
How Traits are Inherited
The science of ½’s since each living animal receives a
Sample ½ of its genetics from its father and a sample ½
of its genetics from its mother.
The process of halving is done by Meiosis
Gene Dominance
One Gene
overshadows
The expression of its
other pair (allele)
We’re heterozygous
(different)
WW and
Ww = White
Recessive Genes
We’re Homozygous
(the same)
•The gene that is
overshadowed by a
dominant gene.
Recessive genes can only
be expressed when they
both are present
RED COAT COLOR = ww
QUALITATIVE TRAITS
TRAITS THAT ARE AFFECTED
BY A SINGLE OR A FEW
PAIR OF GENES
COAT COLOR
TEETH
HORNS
QUANTITATIVE TRAITS
TRAITS AFFECTED BY NUMEROUS
PAIRS OF GENES
The thousands of genes present make
countless combinations possible in an
animal. Since genes are too small to
identify individually, they express their
presence by such outward effects as
differences in growth, carcass or
reproduction traits
Quantitative Traits (cont’d)
Growth traits
Birth weight
Weaning weight
Yearling weight
Growth rate (ADG)
Frame size
Carcass traits
Rib eye area
Fat thickness
Marbling
Reproduction traits
fertility/adaptability
Which buck has the best genetics for growth?
Is the buck on the left bigger because he had
better genetics for growth or because he was
provided a better environment?
IMPROVEMENT OF ANY
TRAIT DEPENDS:
MEASURING DIFFERENCES IN A TRAIT
ACCURATELY IDENTIFYING SUPERIOR
INDIVIDUALS IN THE TRAIT
USING SUPERIOR INDIVIDUALS AS PARENTS
HOW HERITABLE THE TRAIT IS (heritability)
What is Selection?
• Choosing animals to be parents for the next
generation to produce certain characteristics
• Low Birth weight
• Heavier Weaning Weight
• Gaining Fast
• Horned or Polled
• Temperament
• Better Eating Quality
Heritability(h2)
Percentage of the differences (measured or observed) in a trait
between animals that are transmitted to the offspring.
Reproduction
Low
fertility,etc.
Production
Moderate
growth
Product
High
carcass
(Heritability is a measure of how a trait will
respond to selection)
Low Heritable Traits
•
•
•
•
•
Birth Interval
Number Born
Rear Legs
Udder Support
Reproduction
5-10%
15%
15%
20%
15%
Moderately Heritable Traits
•
•
•
•
•
•
•
Birth Weight
Weaning Weight
Yearling Weight
Feed Conversion
Quality Grade
Ribeye Area
Muscling
30-40%
20-30%
40%
40%
40%
40-45%
40-45%
Highly Heritable Traits
•
•
•
•
•
Mature Weight
Milk Fat
Stature, Frame
Carcass Weight
Scrotal Circumference
65%
55%
45-50%
45-50%
50%
Selection for traits is Impacted
by the Correlation(r2)
Between Traits
• Genetic Correlation measures the genetic
association between traits
• Phenotypic Correlation measures the local
or environmental association between traits
• Correlation ranges in value of +1.0 to –1.0
(indicates the direction of association)
Phenotypic Correlations
Body
WT
Length Heart Girth Backfat Loin Area
Kidding
-.50
Difficulty
Length
+.92
Heart Girth +.97
+.87
+.60
+.45
+.51
Loin Area +.90
Scrotal
+.86
Circumference
+.74
+.89
+.79
+.87
+.77
+.51
Backfat
+.67
Use of Heritability and
Correlations
• Selection for Weight makes moderate
progress (h2=40-65%)
• Positive Correlation (r2=+.50) between
birth, weaning and carcass traits means
Selection will result in increases in all
three traits.
Use of Heritability and
Correlations
• Selection for Weight makes moderate
progress (h2=40-65%)
• Negative Correlation (r2=-.50) between
Weight and Kidding Difficulty means
Selection will result with increased
Kidding Difficulty and birth, weaning
and carcass weight.
Selection for the Industry
•
•
•
•
•
Consumer
Packer
Feeder
Commercial producer
Purebred Breeder
• Each section may have differing
trait criteria
CONSUMER
•
•
•
•
•
Price/ Value
Consistency
Holidays
Taste/ Flavor
Safety/ Health
PACKER
• Dressing Percent
• Quality Grade
• Yield Grade
FEEDER
• Health
• Gain
• Feed Efficiency
Commercial or Purebred
Producer
• Reproduction
• Maintenance Cost
• Growth
– Weaning
– Yearling
ECONOMIC
IMPORTANCE
TRAIT
RELATIVE
IMPORTANCE
REPRODUCTION
2
PRODUCTION
1
PRODUCT
1
Heritability
(Heritability is a measure of how a trait will
respond to selection)
Reproduction
Production
Product
Low
Moderate
High
“or how well the offspring resemble their parents phenotype”
MEASURABLE TRAIT
(Phenotype)
• GENETIC EFFECTS
– ½ GENETICS FROM BUCK
– ½ GENETICS FROM DOE
• ENVIRONMENTAL EFFECTS
– WEATHER
– NUTRITION
– HEALTH
– Etc.
Measures of Phenotype
P = G + E
Birth weights
Weaning weights
Yearling weights
Carcass Traits
Reproductive traits
Adaptability
Measures of Phenotype
P = G + E
Requires:
1. Identification of animals
2. Equipment to record trait measure
3. Record Keeping System
4. Computer with Spreadsheet is
economical and recommended
Genetic Evaluations
Phenotypes and Pedigrees
Objective: convert data into genetic
information for the purpose of selection
Separate genetic portion of phenotype from
environment.
41 lbs
•
•
•
•
90 DAYS OLD
ON FARM “A”
BUCK
2 YR DOE
38 lbs
•
•
•
•
105 DAYS OLD
ON FARM “A”
BUCK
4 YR DOE
WHAT ARE THE KNOWN ENVIRONMENTAL EFFECTS?
Known Environmental Effects
650
680
AGE
- 15
DAYS
+ 15 DAYS
AGE OF DOE
2 YR OLD
4 YEAR OLD
FARM
SAME
SAME
Adjusted 90 day wt.
formula
(Actual Wt - Birth wt) X 90 + doe age adj. + birth wt
Age in days
Breed associations are calculating adjustments as they
accumulate data from the breeders
Adjusted 90 day wt.
(41 –8)
90 days
X 90 + 5 + 8
= 45.999 Lbs.
(42 – 7) X 90 + 0 + 7
105 days
= 36.999 Lbs.
Contemporary Group Ratios
adj. 90 day wt
39
Buck A
adj. 90 day wt
37
Buck B
Herd Avg. = 36
Herd Avg.= 36
Ratio = 39/36
Ratio = 37/36
108
102.8
Useful for within herd selections but not between herds
We must expect differences between
animals across different environments
Future Genetic Evaluations
Source of data
Ancestors
Collateral relatives
Descendents
Own performance
Correlated traits
(EPD)-Expected Progeny
Difference
• A prediction of the genetics a goat will pass on to
his kids, when compared to other goats within the
breed
• Takes into account the actual measurements, all
ancestral measurements and environment
• Not a perfect science, so use as a risk
management tool
College Football BCS
Purpose is to identify best college football teams
Source of Data :
AP ranking
USA Ranking
Record
Strength of schedule
etc.
Ranking changes as more games are played
National Goat Evaluation
Breed Specific
Breed summaries report
EPDs.
Expected Progeny Difference
And Breeding Values
The American Boer Goat Association, American Dairy
Goat Association, National DHI Program
Interpreting EPDs
Provide a prediction of future progeny performance of
one individual compared to future progeny of
another individual within a breed for a specific trait.
Allow one to compare or rank the genetic superiority
of individual animals within a breed for a specific
Trait.
EPDs are reported in the actual unit that the trait is
Measured (Lbs. for growth traits).
They can be positive or negative numbers
Effective EPDs: Examples
• Scrotal Circumference (SC)
High SC bucks sire does with earlier Puberty
• Birth Weight (BW)
Low BW bucks have more live kids
• Average Daily Gain (ADG)
Allows choice for replacements or sale of
weanlings
• Carcass Merit (CM)
Allows choice for direct or wholesale Marketing
Avg.
Array of genetic value of an individual
(EPD), adjusted trait performance
Difference in Array for two Bucks
Full Brothers have a sample 1/2 genetics of buck & of the doe but
Not necessarily the exact same genetics
HOW ABOUT
a
BREAK?
How do you use genetic tools in
a selection program ?
Start by using available information
Evaluate Goat Breed Characteristics that
Appear to fit your marketing plan
Average Breeding Values of Six
Dairy Goat Breeds
Breed
Milk
Fat
Protein
Alpine
0
0.0
0.0
LaMancha
-114
-0.7
-1.3
Nubian
-531
4.4
-1.9
Oberhasli
-476
-15.7
-14.3
Saanen
60
0.8
1.9
-6.4
-.35
Toggenburg -18
Alpine
LaMancha
Nubian
You would expect 114 and 531 pounds less milk
From LaMancha and Nubian as compared to Alpine
Oberhasli
Saanen
Toggenburg
When compared to Alpine, you would expect 60 lbs more
Milk for Saanen, 476 lbs less milk from Oberhasli and
18 lbs less milk from Toggenburg
Infant Meat Goat Industry
• Breed Associations are growing
• Members are sending data through
membership
• Information is increasing
• Most selections must come from individual
and herd data
Infant Meat Goat Industry
• Majority of information reports data on
Spanish (brush), Boer, Kiko, San Clemente,
Myotonic (fainting) and crossbreds
• This data provides ranges for comparison
• Emerging breed associations will help
supply needed breeding values
KIKO
Spanish
Common
Meat
Goat
Breeds
BOER
San Clemente
Boer Buck Performance Test
(Langston Univ. & Okla. State Univ., 2004)
Total Gain (lbs)
53.1
27.5-68.2
Average Daily
Gain (lbs per day)
0.63
0.33-0.81
Feed Efficiency
(lbs of feed per lb
of gain)
6.8
5.1-9.3
Loin eye area
(square inches)
1.95
1.29-2.54
Growth Performance
(Langston Univ., 2003)
DM intake
(lb/day)
Avg Daily
Gain (lb)
Feed
Efficiency
(adg/dm feed)
Alpine
1.56
0.13
0.339
Angora
1.05
0.13
0.61
Boer
1.53
0.19
0.559
Spanish
1.13
0.08
0.32
Carcass Performance
(Texas A&M Univ, 1999)
Feedlot
Range
Feedlot
Range
Live Wt
83.97
45.12
73.74
40.52
Carcass
Wt
Back Fat
47.78
22.0
42.33
19.25
.047
.012
.028
.012
Type
11.42
3.25
8.33
1.83
Marbling
3.35
1.70
3.06
1.80
Angora
Cashmere
Common Fibre
Goat Breeds
Mohair Production & Value
Year
Value of
Production
(1000 $)
2003
Goats
Production Price
Clipped
per Unit
(1000 hd) (1000 lbs) (US $)
283
2,174
1.58
2002
283
2,174
1.58
3,432
2001
402
2,628
4.00
10,609
2000
444
2,896
3.00
10,016
1999
700
5,045
2.00
12,562
1998
931
6,814
2.00
15,341
3,435
Putting it Together at this Point
•
•
•
•
•
•
Develop Marketing Plan
Use Breed Characteristics
Evaluate Breeding Values
Gather herd performance data
Compare Animal Performance
Develop Record System
Genetic Selection or
Breeding Plans
Interpreting Adjusted
Performance Traits
These tools predict the average value of
genetic ability offered by an animal.
Available Breeding Tools
• First: Pedigree Evaluations
• Second: Use of Heterosis
• Third: Trait Calculation & Indexes
FIRST
87 ½ % of genetics of kid crop
is a result of last 3 bucks used!!
Buck 1 (50%)
Kid
87 ½ %
Buck 2 (25%)
Doe 1 by buck 2
Buck 3 (12.5%)
Doe 2 by buck 3
FIRST
Calculating Pedigree Estimate
EPDs
Buck (1/2 Trait
Value )
KID
MG Buck (1/4 Trait
Value)
Doe
Pedigree Est. = ½ Buck Value + ¼ MGB Value
FIRST
Calculating Pedigree Estimate
EPDs
Toots (birth value=6.4)
KID
Caesar (birth value=8.8)
Doe
Pedigree Est. Birth value= ½ (6.4)+ ¼ (8.8)= 5.4
SECOND
Benefits of Crossbreeding
Optimizing breed complementarity
Capitalizing Heterosis (Hybrid Vigor)
HETEROSIS (HYBRID VIGOR)
Measure of superior performance of a
trait of the ‘Crossbred individual’ over
and above the average performance
of that trait of the two parental breeds.
breeds
% HETEROSIS
Crossbred Avg. – Parental Breeds Avg. X 100
Parental Breeds Avg.
Heterosis
Cross Bred Boer-Spanish
Reproduction
Breed A
F1 Cross
Breed B
Growth
Carcass
Example of % heterosis:
Breed A avg. weaning weight = 45 Lbs.
Breed B avg. weaning weight = 51 Lbs.
AB crossbred avg. weaning weight = 50
% Heterosis = 50– 48 X 100
48
= 4%
Response to Heterosis
Inversely related to the heritability of the trait
The More diverse differences of breeds used
The greater the response
Types of Heterosis
Individual expressed in the XB kid
Maternal expressed in the doe
Paternal expressed in the buck
Expected % Heterosis
Trait
Individual
Maternal
Kidding %
3.4
6.6
Adaptability
1.7
2.0
Birth wt.
2.7
1.6
Lbs. kid/doe
8.5
14.8
Wean Wt.
4.7
4.2
% of Maximum Heterosis
realized in different crossbred
percentages
Crossbred %
50: 50
50 : 25 : 25
9/16 : 7/16
3/8 : 5/8
5/16 : 11/16
75 : 25
3/16 : 13/16
7/8 : 1/8
% Max. Heterosis
100
100
87.5
75
62.5
50
37.5
25
SECOND
Crossbreeding Systems
To improve:
1.
2.
3.
3.
Lbs. Calf weaned per cow maintained
Adaptability
Live Births
Other Traits of Interest
Basic Two Way Cross
A
B
AB
+ 8.5% Lbs. Kid/Doe
Only capture Individual Heterosis in the Kid
11
Rotational Crossbreeding
2 Breed
A

B

3 Breed

A
B
 
C
Heterosis increases Heterosis increases
lbs. kid per doe
lbs. kid per doe
15%
10
20%
Rotational-Terminal Sire Crossbreeding
A
B
T
11
+23.3 % Lbs. kid/doe
Heterosis in different
crossbreeding systems
% Heterosis in XB Population
System
Does
Two breed
0
2 breed crisscross
67
3 breed rotation
86
3 brd cross terminal 100
Backcross
100
Kids
100
67
86
100
50
lbs kid
wn/doe
8.5
15.6
20.0
23.3
19.0
% Heterosis for Lbs. Wean/Doe
25
% Heterosis
20
15
Ind + Mater
Mater. Het.
Ind. Het.
10
5
0
Ind. Het.
Mater. Het.
Ind + Mater
Maternal & Individual Heterosis is additive
100
Different
Breeds of
Goats
Worldwide
4,950
Combinations
• Two Breed Crosses with 100 different
Breeds
161,200
Combinations
• Three Breed Crosses with 100 Different
Breeds
Use Genetic Tools and
Breeding Values or
EPDs
When Available
Identify bucks that will contribute to
Improvement in economically important traits
PERFORMANCE
BENCHMARKS
What is the current level
of herd performance?
What direction (if any) should
the herd move?
Single Most Important Trait
In The Goat Industry ??
REPRODUCTION
THIRD
Measure of Production/
Reproduction
Lbs kid weaned / doe exposed
= % kid crop weaned X avg. wn. Wt.
Prorates total lbs. kid weaned across all does maintained
Best measure of productivity
THIRD
Lbs. Kid Weaned /
Doe Exposed
% kid crop
Avg. W.W.
Lbs. / doe
120
39
46.8
105
39
40.9
95
39
37.1
85
39
33.2
Where Can I Find
Quality Data ?
Individual herd Owners
Breed Associations
National Dairy Program
Establish Benchmark of
Production
Determine which traits need improvement
Select for that trait(s)
BW= birth weight
WW= weaning weight
SC= scrotal circumference
Adaptability
Identify How to Use Different
Bucks for Different Purposes
Produce Replacement Does
Terminal Cross Bucks
Kidding Ease Bucks
Carcass Merit Bucks
Remember
Genetic Correlations
(Antagonisms)
Milk production, Growth rate (size)
 vs. Fertility
 vs. Maintenance requirements
Quality vs. Red Meat Yield
Growth rate and Calving ease
Birth weight vs. Yearling weight
Use Trait Qualities
Heritability
Heterosis
Reproduction
(fertility)
LOW
HIGH
Production
(growth)
MODERATE
MODERATE
Product
(carcass)
HIGH
LOW
A
B
C
D
-1.1 22
18 43 .48
Which is the “BEST Buck”?
Pick Your Buck
B
A
B=10, W=35, S=39, M=130
B=12, W=42, S=40, M=155
C 5. 7 47
11 90 .09
D
-1.1 22
18 43 .48
B=11, W=38, S=33, M=160
B=15, W=45, S=41, M=170
Brth Ww SC
M
Breed Avg. 11.5 42 33 150
GOOD BUCK?
Don’t Buy a “Billy in a Cart” USE
A Source of Quality Information
Preliminary Selection on
Performance
Then FOCUS on:
-Structural Soundness
-Temperament
-Scrotal Circumference
-ect
STRUCTURAL SOUNDNESS
Skeletal design & how well the bones
support the animal’s body
Related to Longevity
And Adaptability
FEET
LEGS
Correct Structures
Angle of Pastern is usually the same as Angle of Shoulder
Breeding Systems
Develop your Marketing Plan

Choose your breeds: Breeding Values and

Characteristics
In a crossbreeding system, balance the
characteristics of the breeds used.

Choose Bucks with performance data. Use
EPDs when available.

Crossbreeding Considerations
•Systematic crossbreeding has benefits.
–Heterosis; Complementarity
•Planning is critical.
–Use EPDs when available.
•Crossbreeding is NOT a substitute for poor
management.
Action Plan
Selection Considerations
Use Breeding Values as a selection tool when
available.
Target kidding difficulty, growth and doe size genetics
to match environment.
Know your market --- what your herd will “produce”
Adopt a “consumer-focused” mindset towards carcass
merit (avoid misfits).
Characterize strengths and weaknesses.
Consumers
will shape
our future
and set the
Pace!
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