Strategies to maintain genetic diversity in rare breeds of livestock

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Strategies to maintain genetic diversity in rare
breeds of livestock

• Mark Knauer, PhD
• North Carolina State University Swine Extension
  Specialist
• ALBC 11-8-13

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Why is genetic diversity important?

• Genetic diversity and inbreeding are inversely
  related
• Therefore, we work to keep inbreeding at a
  minimum
• What is inbreeding?
• Mating together animals that are related by
  ancestry

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Inbreeding is unfavorable

• Impaired reproduction

Adapted from Bereskin et al. (1968)
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Inbreeding is unfavorable

• Impaired survival

Adapted from Bereskin et al. (1968)
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Inbreeding is unfavorable

• Impaired growth performance

Adapted from Bereskin et al. (1968)
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Inbreeding is unfavorable

• Largest reproductive issue
• Getting females bred continuing the population

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Inbreeding is unfavorable

• Increased incidence of genetic defects
• hermaphrodites

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Other genetic defects
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Calculating inbreeding

• Where
• t generation and
• ?F 1/2Ne
• Where Ne the effective population size

Ft 1 (1 - ?F)t
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Maintaining genetic diversity

• Reduce the rate of inbreeding

Ft 1 (1 - ?F)t
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Avoid mating close relatives

• Avoid mating in order of importance
• Parents and offspring
• Full siblings - brothers and sisters
• ½ siblings ½ brothers and sisters

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Increase your population size
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Increase the number of herd sires used

• Important to use as many males as possible
• Using a couple or several males, instead of just
  1, significantly reduces inbreeding

favorable
unfavorable
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Bring in outside genetics live animals
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What if your new boar is too large/too small for
your females?

• If boar is too small
• Collect semen off of the sow in heat
• Inseminate sow with collected semen
• Use a breeding crate
• If boar is too big
• Train to mount an AI dummy
• Use a breeding crate

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Train to mount an AI dummy
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Use a breeding crate
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Bring in outside genetics semen
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Develop a grade up program
½ heritage

3/4 heritage

7/8 heritage


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Maintaining genetic diversity

• Lengthen the generation interval

Ft 1 (1 - ?F)t
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Generation interval
__

• Where L generation interval

L Lm Lf
______
2
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Lengthen the generation interval

• Do not keep offspring out of gilt litters
• Keep offspring out of old boars and old sows

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Keep offspring out of older parents
Age of boar (yr) Age of sow (yr) Generation interval
Scenario 1 2 1 1.5
Scenario 2 5 4 4.5
Rate of inbreeding is 3 times less in scenario 2
vs. 1.
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Strategies to maintain genetic diversity

• Avoid mating close relatives
• Increase your population size
• Increase the number of males used for breeding
• Bring in outside genetics
• Live animal introductions
• Semen
• Develop a grade up program
• Lengthen the generation interval

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Thank you all for your hard work!

• Maintaining heritage breeds can be challenging
• Important to maintain the genetic diversity
  associated with heritage breeds

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Thank you for your time

• Mark Knauer
• mtknauer_at_ncsu.edu

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Strategies to reduce inbreeding

• Sample outside genetics
• At least once every 3 years
• Lengthen your generation interval
• Retain old sows
• Avoid mating
• Brothers and sisters
• ½ brothers and sisters
• Parents and siblings

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Strategies to reduce inbreeding

• Sample outside genetics
• At least once every 3 years
• Lengthen your generation interval
• Retain old sows
• Avoid mating
• Brothers and sisters
• ½ brothers and sisters
• Parents and siblings

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Strategies to reduce inbreeding

• Sample outside genetics
• At least once every 3 years
• Lengthen your generation interval
• Retain old sows
• Avoid mating
• Brothers and sisters
• ½ brothers and sisters
• Parents and siblings

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Other benefits of using AI

• Genetic improvement
• Only one best herd
• Genetic cost - may be less expensive to use AI
  than maintain a boar
• How many sows do you have?
• Increase number of potential matings
• How many of you have had a boar that was too big
  or too small to breed a desired female?

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Other benefits of using AI

• Genetic improvement
• Only one best herd
• Genetic cost - may be less expensive to use AI
  than maintain a boar
• How many sows do you have?
• Increase number of potential matings
• How many of you have had a boar that was too big
  or too small to breed a desired female?

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Other benefits of using AI

• Genetic improvement
• Only one best herd
• Genetic cost - may be less expensive to use AI
  than maintain a boar
• How many sows do you have?
• Increase number of potential matings
• How many of you have had a boar that was too big
  or too small to breed a desired female?

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Summary

• Multiple potential benefits to adopting AI
• Maintain genetic diversity!
• Genetic improvement
• Reduce genetic cost
• Increase boar usage
• You are taking a positive step today towards the
  benefits of AI technology

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Why should you use AI?

• 1 reason genetic diversity
• Inbreeding causes inbreeding depression which is
  characterized by reduced fitness

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Why should you use AI?

• Inbreeding - the breeding or mating of related
  individuals within a closed group animals
• When is the last time you introduced outside
  genetics into your herd?