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Title: USING GENOMICS TO IDENTIFY GENES AFFECTING RESISTANCE TO NEMATODE INFECTIONS IN RUMINANTS

Author
item Gasbarre, Louis
item Sonstegard, Tad
item Van Tassell, Curtis - Curt
item ARAUJO, RICARDO - EMBRAPA LABEX

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 10/18/2004
Publication Date: 10/20/2004
Citation: Gasbarre, L.C., Sonstegard, T.S., Van Tassell, C.P., Araujo, R. 2004. Using genomics to identify genes affecting resistance to nematode infections in ruminants. In: Mendoza, P. ed. Preceedings of the Mexican Association of Veterinary Parasitologists. October 20-22, 2004, Colima, Mexico. p. 20-26.

Interpretive Summary: THIS IS AN PROCEEDINGS ABSTRACT. NO INTERPRETIVE SUMMARY REQUIRED.

Technical Abstract: Gastrointestinal nematodes infections of grazing ruminants are characterized by a highly skewed distribution of parasite eggs in the feces. A small percentage of animals are responsible for most of the parasites reaching the pastures. This means that transmission of these nematodes can be reduced by identification and management of the few individuals responsible for most of the eggs seeding pastures. To identify the genes coding for parasite resistance we developed a closed-pedigree population of Angus cattle containing 343 parasite-challenged calves derived from 43 sire families. Parasite challenge consisted of a 4-6 month exposure on pastures harboring Ostertagia and Cooperia. Genotypying involved 248 microsatellite markers and 432 animals: the parasite-challenged animals, their parents, and historic sires from the extended pedigree. Phenotypic traits analyzed included mean and peak EPG, the EPG profile, and final serum pepsinogen. GenoProb, a program based on multilocus iterative allelic peeling to calculate probability of allele inheritance for each meiosis in the pedigree, was used to determine inheritance probabilities which were then used to identify quantitative trait loci (QTL) on the bovine chromosomes. Models for analysis included sex of calf, age of dam at calving, age of calf, calving season, and sire. In a sire family model, within-sire regression was calculated based on the probability of inheriting 1of the 2 marker alleles from the sire. QTL were identified on bovine chromosomes, 2, 3, 5, 6, 14, and 15 for EPG, and on chromosomes 3, 11, and 18 for serum pepsinogen. In conjunction with this analsis, we have also developed a 409 gene microarray to identify immune system-related genes showing different levels of expression in resistant or susceptible animals. These data are being combined with current studies involving validation and fine mapping of the QTL to identify the genetic controlling GI nematode resistance in cattle.