Breeding systems
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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.
Breeding systems
- 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.
- 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
- 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