APPLIED GENETICS

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APPLIED GENETICS

• GENES ARE THE BLUEPRINT FOR THE DEVELOPMENT OF
  ORGANISMS

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• THIS BLUEPRINT INTERACTS WITH THE ENVIRONMENT TO
  DETERMINE THE ACTUAL DEVELOPMENT.
• HENCE
• PHENOTYPE GENOTYPE ENVIRONMENT

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GENE ACTION

• ANIMAL CHARACTERISTICS MAY BE DETERMINED BY MANY
  PAIRS OF GENES OR BY ONLY ONE PAIR OF GENES.
• MOST ECONOMICALLY IMPORTANT TRAITS ARE BASED ON
  MULTIGENE INHERITANCE AND ARE ADDITIVE.

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NORMAL DISTRIBUTION CURVE

• MULTIGENE INHERITANCE RESULTS IN A WIDE VARIATION
  IN THE FREQUENCY IN WHICH A PRODUCTIVE TRAIT
  OCCURS.
• THIS RESULTS IN A FREQUENCY DISTRIBUTION CURVE.

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POSSIBLE OUTCOMES IN A FLOCK OF 500 HEAD WHEN
THE TRAIT IS DETERMINED BY 100 DIFFERENT
GENES (LOCI)
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SELECTION

• SELECTION OF ANIMALS WITH SUPERIOR TRAITS WILL
  RESULT IN THE IMPROVEMENT IN THEIR PROGENY ONLY
  IF THEY ARE HERITABLE. THAT IS, THEY ARE
  GENETICALLY RELATED. IF IT IS ENVIRONMENTALLY
  DETERMINED THE SELECTION WILL NOT BE SUCCESSFUL.

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RATE OF GENETIC GAIN

• THIS IS DETERMINED BY
• DEGREE OF HERITABILITY
• SELECTION DIFFERENTIAL
• GENERATION INTERVAL
• ACCURACY OF SELECTION

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GENETIC GAIN

• FORMULA
• GENETIC GAIN
• Selection Differential X Heritability /
  Generation Interval

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IMPACT ON MANAGERS

• Select a smaller of superior animals to
  increase gain
• Ensure accurately assess the characteristic.
  Objective measurement is better.
• Select the animals based on as few
  characteristics as possible.

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LIFETIME PERFORMANCE

• This is influenced by
• Size of the Selection Differential
• The quantity of Repeatability

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HELPFUL AIDS IN SUCCESSFUL SELECTION

• ESTIMATED BREEDING VALUES
• PERFORMANCE OF INDIVIDUAL ANIMALS. EG. FERTILITY,
  DYSTOCIA, GROWTH.
• CORRELATION BETWEEN TWO OR MORE CHARACTERISTICS.
  EG GROWTH RATE AND BIRTH DIFFICULTY.

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GOAL SETTING

• CLEARLY DEFINED GOALS MUST BE EVIDENT.
• SET A PRODUCTION GOAL IE. WHAT MARKET ARE YOU
  AIMING AT.
• DETERMINE BREEDING GOALS. THESE MAY BE BROAD
  STATMENTS INDICATING YOUR INTENT.
• SET SPECIFIC SELECTION CRITERIA

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SELECTION CRITERIA

• PROCESS
• LIST AVAILABLE CRITERIA EG. 200 DAY GROWTH,
  CALVING DIFFICULTY ETC.
• SELECT THOSE WHICH RELATE TO ACHIEVING YOUR
  BREEDING AND PRODUCTION OBJECTIVES.
• .

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• REMEMBER TOO MANY CRITERIA DILUTES THE SELECTION
  DIFFERENTIAL, HENCE REDUCES THE RATE OF GAIN.

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• CULL MALES AND FEMALES BASED ON YOUR SELECTION
  CRITERIA. CONSIDER THE SELECTION PRESSURE THAT
  YOU DESIRE.
• MONITOR PROGRESS LOOK FOR CORRELATIONS AND OTHER
  RELATIONSHIPS AND MODIFY YOUR SELECTION CRITERIA
  APPROPRIATELY