Discriminations Sheep showing evidence of the following fail to meet the breed standard: lack of muscle development or ability to grow and thrive, dark or black or colored fleece, unmanageable disposition, underdeveloped genitalia, split or asymmetrical testicles, upturned vulva, hernia, over or undershot jaw, prolapse or tendency to prolapse (rectal or vaginal), inverted eyelids, weak udder attachments and teat size or placement that impedes nursing. NOTE: The USSA allows for an appendix registry and upgrading to purebred status. When animals reach 15/16th status (purebred) these animals must adhere to the breed standard as well. Sheep that appear to be black faced crossbreds do not meet the Suffolk breed standard. Genetic and Performance Considerations Visual or phenotypic selection has been used for centuries in animal breeding. It does address issues of structural correctness, breed type, sex character, and breed aesthetics. Today, there are additional tools and resources available to quantify and measure traits. Genetic testing can reduce and eliminate genetic recessives (spider syndrome, dwarfism, and scrapie susceptibility). The technology more accurately evaluates genotype and expands the ability to select breed improving replacements. Superior performing animals within a flock can be additionally identified through on farm data collection. This can include such things as weighing (60, 90 or 120 day weights) and ultrasound scanning for carcass traits (loin eye size and fat depth). Another potential strategy is the use of estimated breeding values (EBVs). This tool allows for measurable genetic comparison, over time, and across flocks with other performance recorded flocks. Either of these selection methods (as well as others yet to be developed) can be used as additional tools to measure rapid growth, leanness, and superior muscling – all of which reinforce the Suffolk as the preferred terminal sire breed. Further, as the industry moves toward more objective carcass evaluation, there will be premiums paid for market animals that meet more demanding carcass expectations.
WEBINAR SERIES SUFFOLK JULY 24 - SUFFOLK WEBINAR - SHEEP GENETICS 101 Dr. Joe Emenheiser – www.suffolks.org DECEMBER 5 - RAMS & PROFITABILITY: A PANEL DISCUSSION www.suffolks.org
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Breeders face many challenging decisions as they attempt to produce better sheep for themselves and their customers. Animal breeding uses selection and mating decisions to increase desirable genes and decrease or eliminate undesirable ones. In theory, each generation is better than the last. In reality, an offspring inherits half of its genes from each of its parents, but the half of their own genes that each parent contributes is random. Also, many of the most important traits are controlled by many genes simultaneously, and their expression is subject to environmental effects that are not heritable. This is what makes breeding sheep different from mixing colors of paint - and that challenge can be both fun and frustrating. Fortunately, the inheritance of some of the most serious genetic defects is relatively predictable. In many cases, these conditions are controlled by only a single gene, and their expression is not influenced by the environment. For recessive conditions, the defect is visible when an individual carries two copies of the gene. Modern genetic testing allows the genotype of parents to be known and, for certain conditions, the genotypes of their offspring can be predicted. The following Punnett Squares show the possible offspring genotypes for scrapie resistance, spider lamb syndrome, and dwarfism. Sires and dams each randomly contribute one of the two genes in their own genotype to their offspring. In turn, offspring inherit one gene at random from each of their parents. The combination of these two random genes forms the genotype of the offspring. The four quadrants of the Punnett Square show the range of possible offspring genotype(s), and their relative likelihood, for different matings between parents of known genotype(s).
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