Doctoral Degrees (Animal, Wildlife and Grassland Sciences)

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Browsing Doctoral Degrees (Animal, Wildlife and Grassland Sciences) by Subject "Animal population genetics"

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    The influence of Line 1 Herefords on the global Hereford population
    (University of the Free State, 2012-04) Leesburg, Vicki L. Reisenauer; MacNeil, Michael D.; Neser, F. W. C.
    English: The goal of this research was to document the influence of Line 1 Hereford cattle, developed by the United States Department of Agriculture at its research facility in Miles City, Montana, on Hereford populations in the United States, South Africa, Canada, Australia, Great Britain, and Uruguay. Line 1 Hereford cattle were line-bred at the USDA-Agricultural Research Service station of Fort Keogh in Miles City, Montana since 1934. The dissemination of germplasm from Fort Keogh began with the earliest recorded sales in 1948. Analytical approaches made use of both recorded pedigree and genomic markers. Pedigree records numbering nearly 14 million from the American Hereford Association, and 3 million from the Canadian Hereford Association were randomly sampled five times for each year from 1980-2008. Sampled animals were pseudo-mated to Line 1 sires, inbreeding coefficients of the resulting progeny were calculated and relationships of the sampled individuals to Line 1 were estimated as twice the maximum inbreeding coefficient. The Line 1 Hereford population was found to be ancestral to 82% of the current population of purebred Hereford cattle in the United States. The number of Hereford cattle in the Unites States that were related to Line 1 has increased by more than 2% per year. The greatest concentrations of Line 1 genetics were found in the central and Midwestern regions of the country, but Line 1 genetics were found in 48 of the 50 states. Proportion of Hereford cattle registered in Canada that were related to Line 1 increased from 26% to 68% between 1980 and 2007. Animals recorded in the Canadian Herdbook that had ancestors in the American Herdbook were found in 8 of the 9 provinces and of these, animals related to Line 1 Hereford were found in 6 provinces. Two hundred forty animals sampled from the Line 1 herd at Fort Keogh and 311 sires representative of the Hereford breed in the U.S. were genotyped for 50K SNP. Resulting genotypes were used to assess the probability that the animals sampled from the U.S. population were members of Line 1 Hereford. The average probability of membership was 0.20 and the regression of pedigree relationship on genomic probability of membership was 1.73 ± 0.11 (r = 0.65). A similar analysis of the relationship between Line 1 and a sample of the South African Hereford (n = 36) population was conducted using 34 microsatellite loci. It was found that the probability that South African Hereford cattle were descendants of the Line 1 Hereford population was 0.38 ± 0.08. Pedigree relationship of Hereford cattle registered in South Africa with Line 1 was 24%. Obtaining complete herdbooks from other countries proved infeasible. Therefore, pedigrees of highly used sires were used as inferred from the accuracy of their genetic evaluation for direct effects on weaning weight from Hereford populations in the United Kingdom, Australia, and Uruguay with that of Line 1 Hereford. Those estimated relationships were 0.22, 0.30, and 0.23, respectively. The apparent presence the Line 1 Hereford cattle maintain in Hereford cattle around the world is highly important. The observed relationship of Line 1 Hereford with other Hereford populations is indicative of the far-reaching and profound impact of a long-term research program.