|Chase, Chadwick - Chad|
Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2006
Publication Date: 1/5/2007
Citation: Brenneman, R.A., Chase, C.C., Olson, T.A., Riley, D.G., Coleman, S.W. 2007. Genetic diversity among the angus, the american brahman, the senepol and the romosinuano cattle breeds. Animal Genetics. 38, 50-53. Interpretive Summary: The objective of this study was to determine the genetic diversity present in the cattle breeds under evaluation at the USDA, ARS, SubTropical Agricultural Research Station (STARS) near Brooksville, Florida. The cattle herds consist of the Bos indicus American Brahman developed from animals purchased in the southeastern United States, Bos taurus breeds: the American Angus developed from Wye Plantation stock raised under Florida conditions for five generations, the Senepol developed from live animal importations from St. Croix and two bloodlines of Romosinuano imported as embryos, a graded up line from Costa Rica and a purebred line from Venezuela. Forty-seven animals from each herd were selected by their pedigrees and screened across a set of twenty-six genetic markers, specifically microsatellites. The data were analyzed with a population genetics software program (GenePop v. 3.2a). Traditional coefficient of inbreeding values calculated from five-generation pedigrees corroborated the inbreeding statistic (FIS) calculated from the molecular genetic data. Population substructure (FST) seen as breed isolation was determined, gene flow (NM) or evidence of recent crossing between breeds was estimated, and the genetic distances (DS) that are measures of relatedness or genetic diversity were calculated and compared between all breed combinations based on similarities and differences in the molecular genetic data. The results provide the STARS animal scientists with a measure of genetic differences to compare to the heterosis observed in the crossbreeding of these breeds and potentially a base for more effectively pre-screening new breeds that are being considered for evaluation at the STARS in the future.
Technical Abstract: The objective of this study was to quantify the genetic diversity among the breeds for tropical adaptability traits affecting the performance of beef cattle in the southern United States. Twenty-six microsatellite loci were used to estimate parameters of genetic diversity among a Bos indicus breed, the American Brahman, and three Bos taurus breeds, the American Angus, the Senepol, and the Romosinuano that was comprised of two distinctly separate bloodlines. Forty-seven animals from each of the respective STARS herds were selected by pedigree and sampled as breed or bloodline representatives. Analysis was performed using GENEPOP v3.2a. The genetic differentiation detected between the populations was highly significant (P < 0.001). Exact test for Hardy-Weinberg equilibrium (HWE), Wright's F statistic for estimating within breed relationships (FIS), and traditional inbreeding coefficients by pedigree analysis were calculated for each population. Wright's F statistic for estimating population substructure (FST), gene flow or population isolation (NM), and Nei's genetic distance (DS) were calculated pairwise among all five populations based on frequencies of shared and private alleles at the 26 marker loci. The quantification of these parameters based on molecular genetic techniques and population genetics analyses provides evidence substantiating the historical records of the development of these breeds. The breed relationship inferences based on genetic distance should be considered in the further study of crossbreeding effects and the potential of quantifying the relationship between breed diversity and observed heterosis.