Location: Range and Livestock Research2009 Annual Report
1. A catalog of cattle genes. As a major step toward understanding the biology and evolution of ruminants, the cattle genome was sequenced to ~7x coverage. Scientists from Fort Keogh provided genomic DNA and RNA from numerous tissues to this effort. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 identifiable equivalents found in seven mammalian species. There are many evolutionary breakpoint regions in chromosomes identified by cross-species analysis, but those that are cattle-specific have a higher density of chromosome segment duplications, several types of repetitive elements, and species-specific variants in genes associated with lactation and immune responsiveness. Genes involved in metabolism were found highly conserved, although five metabolic genes are deleted or extensively diverged from their human counterparts. The cattle genome sequence provides a new resource for mammalian genome annotation and for accelerating genetic improvement for milk and meat production.
2. Healthy lean beef. Healthfulness of beef is determined, in part, by its fatty acid composition. Seventy single nucleotide polymorphism markers (SNPs) were used to scan the centromeric portion of chromosome 2 of 328 F2 progeny in a Wagyu x Limousin cross for straits associated with rib-eye area, lipid deposition, composition and palatability of meat. ARS scientists in Miles City, MT found a major QTL with additive effects on fatty acid composition near the centromere of chromosome 2. Results suggest this effect may be due to plieotrophic effects of the myostatin locus and lead to a greater understanding of the genetic control of composition of beef.
3. Reduced cost heifer development. Developing replacement heifers is the second largest cost of beef production. Current recommendations are based on maximizing the probability of conception at about 14 months of age. ARS scientists in Miles City, MT found heifers developed to lower target weights than those traditionally recommended consumed 27% less feed over winter and had improved efficiency throughout the postweaning period and subsequent grazing season. This strategy is estimated to reduce costs of developing each replacement female by more than $31.
4. Moving genes between populations, naturally. Backcrossing is a breeding strategy to introduce new genetic material into established breeds or lines of livestock and poultry. When coupled with marker or gene assisted selection, a specific gene or chromosomal region can be introduced into a new genetic background. It is often intended that the remainder of the genome remain unaffected when using these technologies. The objective was to assess the genomic structure of cattle produced by backcrossing for loci that are unlinked to a specific locus that was being moved from a donor breed to a recipient breed in when the particular genetic variant was not otherwise present. Genotypes of the two parental populations, their F1 progeny, and two subsequent backcross generations of animals were determined at 34 independent loci. There was little evidence to suggest any systematic genome-wide departure from pedigree derived expectation as a result of the breeding system. These data validate the desired intention of a backcrossing program that progressive generations migrate genotypically toward one of the parental types.Elsik, C.G., Gibbs, R., Skow, L., Tellam, R., Weinstock, G., Worley, K., Kappes, S.M., Green, R.D., Alexander, L.J., Bennett, G.L., Carroll, J.A., Chitko Mckown, C.G., Hamernik, D.L., Harhay, G.P., Keele, J.W., Liu, G., Macneil, M.D., Matukumalli, L.K., Rijnkels, M., Roberts, A.J., Smith, T.P., Snelling, W.M., Stone, R.T., Waterman, R.C., White, S.N. 2009. The Genome Sequence of Taurine Cattle: A Window to Ruminant Biology and Evolution. Science. 324:522-528.