Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 2, 2005
Publication Date: July 15, 2005
Citation: Benavides, M.V., Echevarria, F.A., Sonstegard, T.S., Van Tassell, C.P., Gasbarre, L.C. 2005. Validation of genomic regions influencing nematode resistance in a bos taurus x bos indicus cross population [abstract]. American Association of Veterinary Parasitologists Proceedings. p. 56.
A study was performed using 230 Brazilian Brangus cattle (5/8 Aberdeen Angus + 3/8 Nelore) which were exposed to natural challenge of gastrointestinal (GI) parasites. Animals at 12, 18, and 24 months of age were kept under extensive grazing conditions on naturally contaminated pastures during the spring and summer at the Embrapa Southern Brazilian Sheep & Cattle Research Centre in Bage, RS, Brazil (31.3oS 54.1oW). The predominant parasite genera were Haemonchus, Ostertagia, Trichostrongylus and Cooperia spp in the younger animals, while in the adult cattle Haemonchus, Ostertagia and Oesophagostomun were most prevalent. DNA from these animals was used to generate microsatellite marker genotypes for association analyses between egg counts (EPG) and genomic regions on six bovine chromosomes previously identified. These regions were selected because previous work at the USDA, ARS in Beltsville, MD had shown to contain quantitative trait loci (QTL) associated with nematode resistance. Marker genotypes for 12 microsatellite loci were amplified by multiplexing and analyzed by fragment analysis using a ABI 3730 Sequencer. Statistical analyses were performed on a set of 91 progeny from four sires. The results showed that the average logEPG (logEPG+25) was significantly different for the BM8124 microsatellite marker (P=0.045) on BTA6. Year of birth, birth season and sex were significant fixed effects (P<0.001) for this trait. This result confirmed at least one of the parasite resistance QTL detected in earlier studies in the herd at Bage. The genetic composition of these cattle (i.e. a Bos taurus X Bos indicus cross) combined with the different parasite transmission conditions in southern Brazil makes this chromosomal region attractive for further study into the basis of genetic resistance in cattle.