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GENOMIC EVALUATIONS-- AN OVERVIEW
A visit with Dr David Selner -- January 17, 2009
The January 2009 USA Sire summary release coincided with the first publishing of Genomic (DNA mapped) trait evaluations, as released by AIPL, Holstein USA, AJCA, etc. This was the result of a collaborative effort between USDA, seven major AI systems (includingTaurus-Service, Inc), breed associations, universities, and other industry entities concerned with genetic advancement.
"Genetics" as a field of human study began with the curiosity of Gregor Mendel, a Cistercian monk from the 13th century, who discovered basic genetic action from breeding peas in the monastery gardens, and wrote down all his observations. Lord Bakewell, an English landowner with large cattle herds, quantified this further in the 18th century with breeding theories that were influential in the development of many English cattle breeds (Hereford, Angus, Shorthorn, Ayrshire, Jersey, etc). It is from Bakewell and his contemporaries we developed concepts like linebreeding, outcrossing, inbreeding, etc.
Within USDA's Bureau of Animal Industry, research herds developed through the 1940s- 1950s which were used in breed trait comparisons, crossbreeding research, and in the formulation of the first sire summaries-- published as "herdmate" comparisons since 1964 by Animal Improvement Programs Laboratory (AIPL) at Beltsville, MD.
Up to the current decade, the word "genetics" in the dairy industry usually meant "populaiton genetics", which is a more statistical than biological evaluaiton and summarization of traits known to be heritable and easily measured for pedigree relationships. But with the advent of "gene mapping" (done first on mice, then humans, now bovines) we now have "Genome" information, ie, the ability to relate traits observed to physical genes possessed.
The first "Genomic" measurements were done by the Swiss, who were intensely interested in the genetics of Cheese yields, and identified the Kappa Casein gene variants (A and B), verifying that possession of the "B" K/C gene results in 10% higher curd formation (cheese yield) from a given protein and butterfat content milk, than possession of the "A" K/C gene. This research found that 92% of Brown Swiss, 78% of Jersey, but only 19% of Holstein cattle carry the "B" variant for cheese.
The next Genomic breakthrough was identifying the genes indicating possession of various lethal recessive traits-- Pinktooth and Mulefoot in Holsteins, Limber Leg and RVC in Jerseys, Weaver in Brown Swiss. (Later, DUMPS, BLAD, CVM were also found through DNA analysis.) This was a great help in allowing genetic selection for AI sampling and ET production among descendants of known carriers of lethal gene recessives. DNA tests were then developed or are developing for the more desirable dominant and recessive traits-- homozygous polled, red hair color, antibody caseins, etc.
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