2013 Winter Webinar Series: Breeding Better Sheep & Goats Breeding Systems Jeff Semler Extension Educator, AGNR Washington County University of Maryland Extensionjsemler@umd.edu - www.sheepandgoat.com
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.
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.
Breeds• Not like we think of them today.• Selection was unused both by nature and by man.
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.
Landrace• Landraces are usually more genetically and physically diverse than formal breeds.
Robert Bakewell• An 18th century English agriculturalist who introduced stockbreeding methods that transformed the quality of Britains 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”
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.
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
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.
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.
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.
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.
Purpose of Breeding Systems• What you don’t measure you can’t manage• Selecting for desirable traits• Selecting against negative traits• Goals or Targets
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.
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.
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.
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
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.
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 alreadyinbred
Inbreeding• Wye Angus• Genetic Abnormalities – Dwarfism in cattle and sheep – Congenital Cardiac Defect in Pygmy Goats – Umbilical Hernia – Tying up in horses
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.
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.
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.
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.
Crossbreeding• Optimize the amount of hybrid vigor.• Produce a uniform product.
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.
Heterosis in Crossbred Lamb Trait Percent HeterosisBirth weight 3.2Weaning weight 5.0Pre-weaning ADG 5.3Post-weaning ADG 6.6Yearling weight 5.2Conception rate 2.6Prolificacy of dam 2.8Lamb survival 9.8Carcass traits 0Lambs reared/ewe exposed 15.2Weight of lamb weaned/ewe 17.8Source: Nitter, G. 1978. Breed utilization for meat production in sheep. Anim. Breed.Abstr. 46:131.
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.