This document summarizes a presentation on breeding systems for sheep and goats. It discusses purebreeding, inbreeding/linebreeding, outcrossing, crossbreeding, and heterosis. Specific breeding systems covered include two-breed crosses, rotational crosses, and terminal crosses. Advantages of crossbreeding include hybrid vigor, utilizing complementarity between breeds, and producing a uniform product. The document provides examples of historic sheep and goat breeds and influential breeders like Robert Bakewell.

1. 2013 Winter Webinar Series: Breeding Better Sheep & Goats
Breeding Systems
Jeff Semler
Extension Educator, AGNR
Washington County
University of Maryland Extension
jsemler@umd.edu - www.sheepandgoat.com

2. Breeding Systems
• Animal breeding is a segment of animal
science that addresses the evaluation of the
genetic value of domestic livestock.
• A breed is a group of domestic animals with a
homogeneous appearance, behavior, and
other characteristics that distinguish it from
other animals.

3. Breeding Systems
• Purebreeding
• Inbreeding/Linebreeding
• Outcrossing
• Cross Breeding
• Single Trait Selection
• Balanced Trait Selection

4. Breeds
• Sheep and goats were domesticated 10,000
years ago in Central Asia.
• These animals helped to make the spread of
civilization possible.
• Shepherding was well-established during
Biblical times.
• There are many references to sheep and goats
in the Bible.

5. Breeds
• Not like we think of them
today.
• Selection was unused
both by nature and by
man.

6. Landrace
• A local variety of a
domesticated animal species
which has developed largely
by natural processes, by
adaptation to the natural and
cultural environment in
which it lives.
• It differs from a formal breed
which has been selectively
bred deliberately to conform
to a particular formal, pure
breed standard of traits.

7. Landrace
• Landraces are usually more genetically and
physically diverse than formal breeds.

8. Robert Bakewell
• An 18th century English agriculturalist who
introduced stockbreeding methods that
transformed the quality of Britain's cattle, horses
and sheep.
• As time progressed, Bakewell became famous for
his "New Leicester" sheep and rented out his
rams for high fees.
• “Like begets like”

9. Breed
• A specific group of domestic animals with a
homogeneous appearance, behavior, and
other characteristics that distinguish it from
other animals or plants of the same species,
and arrived at through selective breeding.
• Despite the centrality of the idea of "breeds"
to animal husbandry, there is no scientifically
accepted definition of the term.

10. Breed
• A breed is therefore not an objective or
biologically verifiable classification, but
instead a term of art amongst groups of
breeders who share a consensus around what
qualities make some members of a given
species members of a nameable subset.
• When bred together, animals of the same
breed pass on these predictable traits to their
offspring, and this ability—known as
"breeding true"—is a requirement for a breed

11. Oldest Sheep Breed
• The Karakul may be the
oldest breed of
domesticated sheep.
• Archeological evidence
indicates the existence of
the Persian lambskin as
early as 1400 B.C. and
carvings of a distinct
Karakul type have been
found on ancient
Babylonian temples.

12. Oldest Sheep Breed
• The Karakul is native to
Central Asia and is
named after a village
called Karakul which lies
in the valley of the Amu
Darja River in the
former emirate of
Bokhara, West
Turkestan.

13. Oldest Breed of Goats
• The domestic goat (Capra aegagrus hircus) is a
subspecies of goat domesticated from the wild
goat of southwest Asia and Eastern Europe.
• Domestic goats are one of the oldest
domesticated species.
• For thousands of years, goats have been used
for their milk, meat, hair, and skins over much
of the world.

14. Oldest Breed of Goats
• The Nubian type
goat is most likely
the oldest breed of
goat known to
mankind.
• The name "Nubian"
originates from
Nubia, a desert
region in Northern
Sudan.

15. Purpose of Breeding Systems
• What you don’t measure
you can’t manage
• Selecting for desirable
traits
• Selecting against
negative traits
• Goals or Targets

16. Pure Breeding
• Pure-breeding is the mating of males and
females of the same breed or type.
• A purebred flock can be managed as a single
flock because all animals are of the same
breed.
• The goal of purebred production is to provide
superior genetics to the commercial sheep
industry.

17. Inbreeding and Outbreeding
• Various mating schemes of animals are
classified under two broad categories —
inbreeding and outbreeding.
• Classification depends on the closeness of the
biological relationship between mates. Within
each category, a wide variation in intensity of
this relationship exists.

18. Inbreeding and Outbreeding
• A very fine line separates the two categories.
• With less closely related animals (first cousins,
second cousins), people disagree about where
to draw the line between inbreeding and
outbreeding.
• Matings between animals less closely related
than this, then, would constitute outbreeding.

19. Inbreeding
• Mating closely related animals (for example,
parent and offspring, full brother and sister or
half brother and sister) is inbreeding.
• Technically, inbreeding is defined as the mating
of animals more closely related than the average
relationship within the breed or population
concerned.
• Also called linebreeding

20. Inbreeding
• Development of highly productive inbred lines of
domestic livestock is possible.
• Although occasional high performance animals
are produced, inbreeding generally results in an
overall reduction in performance.
• This reduction is manifested in many ways.
• The most obvious effects of inbreeding are
poorer reproductive efficiency including higher
mortality rates, lower growth rates and a higher
frequency of hereditary abnormalities.

21. Inbreeding
• Full brother-sister mating 25%
• Half brother sister mating 12.5%
• Father-daughter 25%
• Granddam-grandson 12.5%
• Common grandparents (cousins) 6.25%
*it is assumed that the parents are not already
inbred

22. Inbreeding
Trait Inbreeding Depression
Milk 5%
Growth 3%
Offspring Born 4%
Offspring Weaned 10%

23. Inbreeding
• Wye Angus
• Genetic Abnormalities
– Dwarfism in cattle and sheep
– Congenital Cardiac Defect in Pygmy Goats
– Umbilical Hernia
– Tying up in horses

24. Outcrossing
• The mating of an individual to another in the
same breed that is not related to it.
• This is the most widely used mating system by
both commercial and seedstock producers.
• Outcrossing produces a higher level of
heterozygosity.

25. Outcrossing
• Round Oak Rag Apple Elevation
• During his lifetime, Elevation’s progeny included
more than 10,000 registered sons and nearly
60,000 registered daughters.
• His 650,000 straws of semen generated some
300,000 calves, making him the first million-dollar
inseminator.
• He had the highest number of daughters that
produced 100,000 pounds of milk in their
lifetime, and the highest number of daughters
that lactated more than 30,000 pounds of milk in
a single year.

26. Crossbreeding
• The practice of crossbreeding is a well accepted
practice among sheep producers in the U.S. as
evidenced by the fact that the majority of lambs
marketed each year are crossbreds.
• Crossbreeding is used in order to take advantage
of the different and complementary strong points
of two or more breeds and to utilize hybrid vigor.
• However, much of the crossbreeding in the sheep
industry is haphazard, does not utilize systems
that optimize the advantages of crossbreeding,
and are not sustainable over several years.

27. Crossbreeding
• Easy to implement and maintain – The KISS
(Keep It Simple, Stupid) approach applies
here.
• Properly utilize the strong points of different
breeds.
• A well designed crossbreeding system utilizes
these breed differences in a strategic manner
to improve the efficiency of meat, wool, and
milk production over purebreeding.

28. Crossbreeding
• Optimize the amount of hybrid vigor.
• Produce a uniform product.

29. Crossbreeding
• Another advantage of crossbreeding lies in the
ability to utilize breed complementarity.
• All breeds have strengths and weaknesses.
• No one breed excels in all relevant traits.
• Thus, production can be optimized when
mating systems place breeds in roles that
maximize their strengths and minimize their
weaknesses.

30. Heterosis in Crossbred Lamb
Trait Percent Heterosis
Birth weight 3.2
Weaning weight 5.0
Pre-weaning ADG 5.3
Post-weaning ADG 6.6
Yearling weight 5.2
Conception rate 2.6
Prolificacy of dam 2.8
Lamb survival 9.8
Carcass traits 0
Lambs reared/ewe exposed 15.2
Weight of lamb weaned/ewe 17.8
Source: Nitter, G. 1978. Breed utilization for meat production in sheep. Anim. Breed.
Abstr. 46:131.

31. Crossbreeding
• Hybrid Vigor

32. Heterosis in Crossbred Ewe
Trait Percent Heterosis
Fertility 8.7
Prolificacy 3.2
Pre-weaning ADG 5.3
Body weight 5.0
Lamb birth weight 5.1
Lamb weaning weight 6.3
Lamb survival 2.7
Lambs born/ewe exposed 11.5
Lambs reared/ewe exposed 14.7
Weight of lamb weaned/ewe 18.0
Source: Nitter, G. 1978. Breed utilization for meat production in sheep. Anim. Breed.
Abstr. 46:131.

33. Crossbreeding
• Two Breed Cross
• Rotational Cross
• Terminal Cross

34. Crossbreeding
• Two Breed Cross

35. Crossbreeding
• Rotational Cross
• Uses 3 or more breeds
• Should not be too complex
• May result in a composite breed

36. Crossbreeding
• Terminal Cross

37. Review
• Many crossbreeding systems are difficult to
accomplish in a small flock, which may only
have the option of one or two breeding
groups.
• The purchase of replacement females would
enable the use of a terminal crossing program.
• Alternating the use of ram and ewe breeds
would maintain maternal and growth
characteristics in the flock.

38. Questions