Strategies to maintain genetic diversity in rare breeds of livestock Mark Knauer, PhD North Carolina State University Swine Extension Specialist ALBC

Why is genetic diversity important? u Genetic diversity and inbreeding are inversely related u Therefore, we work to keep inbreeding at a minimum –What is inbreeding? v Mating together animals that are related by ancestry

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

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

Inbreeding is unfavorable u Impaired growth performance Adapted from Bereskin et al. (1968)

Inbreeding is unfavorable u Largest reproductive issue –Getting females bred & continuing the population

Inbreeding is unfavorable u Increased incidence of genetic defects –hermaphrodites

Other genetic defects

Calculating inbreeding u Where –t = generation and –∆F = 1/2N e v Where N e = the effective population size F t = 1 – (1 - ∆F) t

Maintaining genetic diversity u Reduce the rate of inbreeding F t = 1 – (1 - ∆F) t

Avoid mating close relatives u Avoid mating – in order of importance –Parents and offspring –Full siblings - brothers and sisters –½ siblings – ½ brothers and sisters

Increase your population size

Increase the number of herd sires used u Important to use as many males as possible u Using a couple or several males, instead of just 1, significantly reduces inbreeding favorable unfavorable

Bring in outside genetics – live animals

u If boar is too small –Collect semen off of the sow in heat v Inseminate sow with collected semen –Use a breeding crate u If boar is too big –Train to mount an AI dummy –Use a breeding crate What if your new boar is too large/too small for your females?

Train to mount an AI dummy

Use a breeding crate

Bring in outside genetics – semen

Develop a grade up program ½ heritage × × 3/4 heritage × × 7/8 heritage

Maintaining genetic diversity u Lengthen the generation interval F t = 1 – (1 - ∆F) t

Generation interval u Where L = generation interval L = L m + L f 2 ______ __

Lengthen the generation interval u Do not keep offspring out of gilt litters u Keep offspring out of old boars and old sows

Keep offspring out of older parents Age of boar (yr)Age of sow (yr)Generation interval Scenario Scenario Rate of inbreeding is 3 times less in scenario 2 vs. 1.

Strategies to maintain genetic diversity u Avoid mating close relatives u Increase your population size u Increase the number of males used for breeding u Bring in outside genetics –Live animal introductions –Semen u Develop a grade up program u Lengthen the generation interval

Thank you all for your hard work! u Maintaining heritage breeds can be challenging –Important to maintain the genetic diversity associated with heritage breeds

Thank you for your time Mark Knauer

Strategies to reduce inbreeding u Sample outside genetics –At least once every 3 years u Lengthen your generation interval –Retain old sows u Avoid mating –Brothers and sisters –½ brothers and sisters –Parents and siblings

Strategies to reduce inbreeding u Sample outside genetics –At least once every 3 years u Lengthen your generation interval –Retain old sows u Avoid mating –Brothers and sisters –½ brothers and sisters –Parents and siblings

Strategies to reduce inbreeding u Sample outside genetics –At least once every 3 years u Lengthen your generation interval –Retain old sows u Avoid mating –Brothers and sisters –½ brothers and sisters –Parents and siblings

Other benefits of using AI u Genetic improvement –Only one “best” herd u Genetic cost - may be less expensive to use AI than maintain a boar –How many sows do you have? u 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?

Other benefits of using AI u Genetic improvement –Only one “best” herd u Genetic cost - may be less expensive to use AI than maintain a boar –How many sows do you have? u 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?

Other benefits of using AI u Genetic improvement –Only one “best” herd u Genetic cost - may be less expensive to use AI than maintain a boar –How many sows do you have? u 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?

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

Why should you use AI? u 1# reason – genetic diversity u Inbreeding causes inbreeding depression which is characterized by reduced fitness

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