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VAP Test 1
Genetics- Animal Breeding
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Juane Boshoff
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Animal breeding
Selection of the best
parents
for the
next
generation
Animal breeding is not the same as
reproduction
Breeding goals
Select
adapted
animals (breeds) to a specific
environment
Adapted
animals =
fertile
/ reproduce
Growth
/
products
Product quality
Phenotype
(P)
How the animal looks,
performance
Genotype
(
G
)
Genetic
composition of the animal,
DNA
Environment (E)
All non-genetic factors that impact the animal, including nutrition, parasites, climate, age of
dam
,
birth status
, gender
Phenotype =
Genotype
+
Environment
The best
genetics
will perform superior in a given
environment
Genetic variability is random in nature due to
random segregation
and
independent
assortment
Variation
is crucial for
survival
An animal's superior performance might be due to either superior
genetics
or a favourable
environment
In a given environment, the animal with
superior
genetics will always outperform the
inferior
genes
Selection
Choosing and growing specific individual animals with
desirable
characteristics
Trait
Observable
/
measurable
characteristic
Phenotype
Measured level of
performance
for a trait
Categories of traits
Fitness
Production
Quality
Type
Behavioral
Fitness traits
Litter size, ovulation rate, calving interval, survivability
Production
traits
Weight, growth rate,
milk yield
,
greasy fleece yield
Quality traits
Meat tenderness, butterfat, fibre diameter
Type traits
Udder
conformation
,
legs
, functional efficiency
Behavioral traits
Temperament,
learning ability
,
milk speed
Traits may be
species
/
breed specific
Breed specific traits
Polled
trait in cattle,
fleece
traits in goats and sheep, performance in race horses
Animal recording
Integrates animal identification and
registration
, animal
traceability
, animal health information and animal performance data
Animal recording
is an information tool to select the best
parents
for the next generation
Animal recording process
1.
Identification
system
2.
Recording
of data (pedigree & performance & dates)
3.
Information
system (manage data)
4.
Data
analyses (on farm – index)
5.
Genetic
evaluation (Breeding values)
6.
Application
of the results (EBV and or selection indices)
7.
On Farm
selection
Recording starts with an
identification number
and
pedigree
Identification methods
Notching
, tags,
tattoos
Practical example of animal recording
Calf is born, weigh the calf, identify the calf and parents, send in
birth notification
, record
cow info
, record calf post-weaning
Traits recorded
Reproduction
data (conception rate, calving rate, number of
offspring
)
Production
data (pre-weaning growth,
post-weaning
weight, quality traits)
Body measurements
(height,
length
, scrotal circumference, udder conformation)
Recording and storage of data can be
paper-based
,
electronic devices
, or specialized software
What we do with the data
1. Use
contemporary
groups for comparison
2. Calculate
genetic parameters
3. Estimate
breeding values
4. Develop
selection indices
5. Breeders perform
objective
and
accurate
selection
Selection is not a
simple process
, it requires setting objectives,
animal recording
, and statistical analyses
Contemporary groups
Groups of animals influenced by the same known and unknown
environmental
effects, used for objective comparison of
traits
Contemporary groups need to have at least 5 animals per group, and be correctly adjusted for
sex
,
birth
status, and age of dam
Contemporary
groups will
differ
depending on the species
Sheep
& pigs –
birth
status more important than in cattle
Some production systems may have
more than one
breeding season – number of seasons may
differ
Additional management inputs e.g. feeding of
preferential
treatment will add to the
contemporary
groups
Contemporary groups need to have
At least
5
animals per group (more always better)
Correct / adjust for
sex
,
birth
status
Use less levels for i.e.
age
of dam
Never form a group on a
trait
that you want to evaluate
Aim is to "compare green apples with green apples"
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