Historical perspectives on genetic fitness research - PowerPoint PPT Presentation

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Historical perspectives on genetic fitness research

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The state or condition for being fit; suitability or appropriateness ... The extent to which an organism is adapted to or able to produce offspring in a ... – PowerPoint PPT presentation

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Title: Historical perspectives on genetic fitness research


1
Historical perspectives on genetic fitness
research
ADSA Pioneer
2
Fitness (Dictionary.com)
  • The state or condition for being fit suitability
    or appropriateness
  • Good health or physical condition
  • The extent to which an organism is adapted to or
    able to produce offspring in a particular
    environment

3
Common understandingof fitness traits
  • Nonproduction
  • Functional
  • But what makes a dairy cow more fit and
    functional than production?
  • We may strain the dictionary definition, but we
    know what we mean

4
Conformationor type
  • Anecdotal observations for eons
  • What we thought cow should look like
  • Linear scoring began around 1980
  • Promoted research on real value of type traits

5
Longevity
  • Justification for type emphasis
  • Direct observation
  • Indicator traits

6
Somatic cell/mastitis
  • SCS is convenient trait for selection for reduced
    mastitis
  • Clear importance and relatively ready acceptance
    of research
  • Like yield, obvious milking-to-milking impact on
    income (profit)

7
Fertility
  • Should we have foreseen problems?
  • Some natural selection
  • Tribolium pupa weight study (1976)
  • Negative response in family size
  • Eventual extinction by generation 16

8
Calving ease
  • Giving birth is most traumatic time in a cows
    life
  • Can minimize negatives by reducing calvings or by
    mating plan
  • Better yet, reduce frequency of bad genes
    (daughter calving ease)

9
Genetic evaluations
10
Indexes
  • Consider all traits with a single number
  • Vital with so many traits
  • Needs to be appropriate for market
  • Needs to be reasonably accurate
  • Many correlated traits complicate process

11
History of USDA indexes
  • Traits Year
  • Milk, fat 1971
  • Protein, solids-not fat 1976
  • Productive life, somatic cell score 1994
  • Type composites 2000
  • Daughter pregnancy rate, 2003
  • calving ease
  • Stillbirths 2006

12
Deleterious genes
  • Mulefoot
  • Bovine leukocyte adhesion deficiency (BLAD)
  • Uridine monophosphate synthase deficiency (DUMPS)
  • Complex vertebral malformation (CVM)
  • Weaver
  • Limber leg
  • Rectovaginal constriction (RVC)

13
Learning from history
  • Obsession with production
  • Low heritability vs. no heritability
  • High economic value
  • Large variation
  • Breed for yield, cull for function
  • We got what we asked for

14
Learning from history (cont.)
  • Beware of pendulum swinging too far back
  • Theoretically, index weights based on research ?
    correct index ? optimum progress
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