|Van Tassell, Curtis|
|Padilha, Terezinha - USDA/EMBRAPA MD|
Submitted to: Animal Genetics International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 2, 2002
Publication Date: August 11, 2002
Citation: GASBARRE, L.C., SONSTEGARD, T.S., VAN TASSELL, C.P., PADILHA, T. DEVELOPMENT OF A RESOURCE POPULATION TO DETECT QTL AFFECTING RESISTANCE TO GASTROINTESTINAL PARASITES OF CATTLE. ANIMAL GENETICS INTERNATIONAL CONFERENCE PROCEEDINGS. pp. 79, 2002. Technical Abstract: Gastrointestinal nematodes severely reduce the efficiency of raising cattle on pasture. Genetic management of 15-25% of cattle can considerably reduce parasite transmission in cattle herds. A selection program was initiated using parental stock from Wye Angus of the U of MD. To date »350 progeny covering 4 generations have been phenotyped. Pedigree records trace back to the founding animals of the herd, and pedigree analysis reveals that >90% of the tested animals are paternally descended from a Wye bull born in 1944. DNA for genetic analysis has been acquired from all tested animals and from over 70 sires in the historic pedigree. Phenotyping is accomplished by placing weaned calves on pastures infected with the 2 most common nematode parasites of US cattle. Calves are monitored weekly for 19 physiologic measures. After at least 120 days on test, calves are selected for replacement breeders, re-challenge, or immediate kill. At kill an additional 23 immunologic or parasitologic measures are recorded. Calves are assigned as: 1) Type I- always low parasite eggs per gram of feces (EPG) values, 2) Type II - increasing EPG values followed by a drop to levels of Type I calves, and 3) Type III - consistent high EPG levels. Reinfected calves show secondary EPG values consistent with those observed during the primary exposure. The selection has increased the percentage of Type I and Type III calves, and the range of EPD values has been reduced to 0.5 of the mean EPG value.