Scientists at USDA’s Roman L. Hruska U.S. Meat Animal Research Center (USMARC) in Clay Center, NE, have discovered a location on bovine chromosome 20 associated with the incidence of the most prevalent bacterial diseases – pinkeye, foot rot and bovine respiratory disease (BRD) – that affect feedlot cattle.

BRD accounts for 75% of feedlot illnesses and up to 70% of all deaths, with economic losses to cattle producers exceeding $1 billion annually. The estimated costs for pinkeye are $150 million yearly, and losses to dairy producers due to foot rot range from $120-$350/animal.

Eduardo Casas, research leader of the Ruminant Diseases and Immunology Research Unit at the Agricultural Research Service National Animal Disease Center in Ames, IA, examined the genetic makeup of cattle for evidence of genes associated with resistance or tolerance to diseases.

Casas and his colleagues combined pinkeye, foot rot and BRD to represent overall pathogenic disease incidence. They developed half-sibling families from crossbreed bulls: a Brahman-Hereford, a Brahman-Angus, a Piedmontese-Angus and a Belgian Blue-MARC III (part Red Poll, Pinzgauer, Hereford and Angus). An analysis of DNA samples from the 240 offspring infected with one or more of the diseases revealed a genetic marker, called a quantitative trait locus (QTL), on chromosome 20. This QTL is associated with the three diseases.

Chromosome 20 is located near genetic markers related to other diseases and may have a significant effect on the overall health of cattle, Casas says. Identifying genetic markers responsible for disease would provide an opportunity to produce cattle with increased disease tolerance, which also could help reduce economic loss associated with diseases.

Read more on this research at www.ars.usda.gov.