Inbreeding and Longevity in Bernese Mountain Dogs

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Inbreeding and Longevity in Bernese Mountain Dogs

• Pat Long and Bert Klei PhD

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Coefficient of Inbreeding (COI)

• Scientific The probability that two alleles at a
  locus are identical by descent.
• Practical The chance that the two copies of a
  chromosome in an animal are coming from the same
  ancestor.
• Practice If the dam and the sire are related the
  resulting puppies will be inbred. The COI
  depends on the level of relationship between the
  sire and the dam.

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Why do We Mate Relatives?

• It happened by accident.
• We did not know that animals were relatives.
• We cannot avoid it.
• It can happen by design.

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Effects of Inbreeding

• Reduced fertility
• Increase in genetic disorders
• Lower birth rates
• Loss of immune system function
• Lower growth rates
• Reduced longevity
• Standard Poodles 1 increase in inbreeding
  results in 1 month shorter life span (Armstrong,
  2000)

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Examples of Matings and Resulting COI

• Full Sib COI 25
• Parent Off-Spring COI 25
• Half Sib COI 12.5
• Uncle Niece COI 12.5
• First Cousins COI 6.25

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Example
4
2
5

• Individual 1 is the result of a half sib mating.
  We can draw a path from 1? 2 ? 5 ? 3 ? 1
• 5 is the common ancestor, or the ancestor to
  which we are line breeding.
• It took us 4 steps to get from 1 back to 1.
• COI(1) is ½(4-1)0.12512.5

1
6
3
5
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Lets Add Two Generations

• Based on this information none of the new
  ancestors are related.
• The only path that can be drawn from 1 to 1 is
  through 5.
• COI(1)12.5

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What Happens with One More Generation

• There is additional information in a data base.
  Male 25 is the father of 14 and 21, female 26 is
  the mother of 13, 18, and 24.

• We can draw paths from 1 to 1 through 5, and new
  ones through 25 and 26.
• This is pedigree information most people might
  not remember.
• COI(1)13.28
• Since the common ancestors occurred many
  generations ago the impact is small.
• COI(2)COI(3)0.78
• It can add up if many common ancestors occur.

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Real Life Pedigree Example

• 45 generations
• 774 ancestors
• 10 generations in which all ancestors are known
• COI36

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Longevity

• In this context Simply the number of days
  between a dogs reported birth and an animals
  reported death regardless of the cause of death
  as reported to Berner Garde

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BernerGarde

• First information collected in the 1970s.
• Official start 1984
• Named Berner Garde in 1993
• Incorporated in 1995
• Mission Ensure a long and healthy lifespan for
  the breed through the collection and
  dissemination of genetic disease information for
  research purposes
• At the end of 2008
• 58,638 animals
• 6,033 with longevity information

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Number of Dogs Registered in Berner Garde by
Birth Year
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Number of Berner Garde Data Submissions By Year
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Age Distribution
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Median Age By Birth Year(Dogs had opportunity to
reach 12 years of age)
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Methods

• Tabular method to calculate inbreeding (Emik and
  Terrill, 1949).
• Linear models to determine the effect of
  inbreeding on longevity taking into account the
  effect of
• Birth Year
• Sex
• Pet vs Breeding Dog Status
• Inbreeding

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Data Used

• All individuals for calculating COI (60,000)
• Individuals with at least 8 generations of
  complete ancestor information for determining the
  relationship between inbreeding and longevity
  (789 dogs).

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Example Revisited
Number of Generations COI Estimate
4 25
8 29
10 29
15 35
20 36
ALL 36

• The more generations of ancestry information that
  are available the higher the estimate of the COI.
• Estimates of COI based on a reduced number of
  generations are always underestimating the true
  COI.

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Known Ancestor Information and Inbreeding
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Results Inbreeding(Only dogs with at least 8
completely known generations)
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Average COI by Birth Year(at least 8 complete
generations of pedigree information)
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Selecting Data

• By restricting ourselves to dogs with 8 or more
  complete generations of ancestry information we
  selected data.
• Selecting data can affect the results of the
  analysis.
• Need to make sure that our selected longevity
  data is a representative sample of all the
  available longevity data.

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Age Distribution for All Available Dogs
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Longevity Data Analyzed
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Median Longevity by COI Class(at least 8
complete generations of pedigree information)
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Methods

• The longevity data is bi-modal
• Split the data
• 79 dogs dying before 2 years of age.
• 710 dogs dying after 2 years of age.
• Analyze them in two separate analyses

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ResultsOlder than 2 Years of Age

• Ave COI 17.8
• For every 1 increase in inbreeding a dog lives
  on average 20.6 days shorter (p0.0007)
• Females live 147 days longer than males (p0.02)
• Breeding dogs live 134 days longer than pets
  (p0.05)

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ResultsYounger than 2 years of age

• Ave COI 17.8
• For every 1 increase in inbreeding a dog lives
  on average 9.2 days shorter (p0.05)
• No difference in males vs females
• No difference in pets vs breeding dogs

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ConclusionsLongevity

• Median Longevity of Bernese Mountain Dogs is 8
  years.
• Median Longevity has slightly increased since
  1984.
• The data shows a period of early death (lt 2 years
  of age) followed by death occurring around median
  age.

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ConclusionsInbreeding

• When determining inbreeding the number of
  complete generations of pedigree information is
  important.
• Average inbreeding in Bernese Mountain Dogs is
  between 15 and 20.
• The trend in inbreeding shows a slight decrease.

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ConclusionsInbreeding Longevity

• Inbreeding does affect the longevity of Bernese
  Mountain Dogs.
• 1 inbreeding results on average in a loss of 20
  days of longevity for dogs dying after 2 years of
  age. Nine days for those dying before 2 years of
  age.
• Other results from the analysis.
• Females tend to live longer than males.
• Breeding dogs tend to live longer than pets.

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Acknowledgements

• Berner Garde Board
• Gary Galunas
• Evan Klei
• All Berner owners who submitted data to Berner
  Garde.