Browsing by Author "Kimberling, Cleon V., committee member"
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Item Open Access Epidemiology of reported scrapie in the United States: 1947-1991(Colorado State University. Libraries, 1993) Wineland, Nora E., author; Salman, M., advisor; Kimberling, Cleon V., committee member; Gould, Daniel H., committee member; Weber, Stephen, committee memberData collected in support of the United States Department of Agriculture (USDA) scrapie eradication program between 1947 and September 30, 1991 were evaluated to determine the presence of trends or patterns which might help further the understanding of natural sheep scrapie. The USDA records from 957 confirmed positive cases of natural scrapie in 581 flocks from 39 states were reviewed and compiled into a database. Possible host and management risk factors for scrapie such as age at death, within-flock mortality, breed, sex, sire and dam disease status, flock size, and location were examined. There were several significant findings from the study. The proportion of reported positive flocks in those states reporting positive cases showed a steady increase between 1965 and 1991. In addition, the average flock mortality showed a slight increase between 1947 and 1991. These increases did not seem to be directly related to any changes in the USDA eradication program. The average age at death for confirmed cases was 43.6 months. Rams died of scrapie an average of five months younger than did the ewes. This difference was statistically significant, but likely due to the small numbers of rams included in the study. There were insufficient numbers of twins (26 pairs) to allow any significant conclusions to be drawn. There were no statistically significant differences between age at death for the eight geographical regions or the various sheep breeds affected. The Suffolk breed comprised 88% of the reported cases, and Hampshire sheep accounted for 6% of the cases. Attempts were made to further define the role of vertical transmission in natural scrapie. The scrapie disease status of the sire had no appreciable effect on the age of death of positive offspring. The scrapie disease status of the dam had a detectable effect with positive offspring from positive dams diagnosed at a significantly younger age than positive offspring from other dams. Unfortunately it was not possible to determine when a positive dam might begin shedding the scrapie agent and consequently present a threat to her offspring. All of the positive dams in the study gave birth to their positive offspring in flocks where there were other active cases of scrapie which might have been the source of infection for the offspring. The source of infection could not be determined for over half of the reported cases. Several possible explanations for this situation were presented. Failure to detect the sources of infection may in part be responsible for the apparent increase in the magnitude of the scrapie problem in the United States. Data quality and consistency was a major issue for this study. The records available from the technical program staff of USDA contained varying amounts of information about each of the positive animals and flocks. In addition to variation in the records, the eradication program itself went through several phases during the study period. These different phases may have had multiple effects on the levels of disease reported to USDA. Unfortunately these effects could not be measured or corrected for in the analysis.Item Open Access Factors that impact probability of pregnancy when using AI boars(Colorado State University. Libraries, 2013) Kaysen, Brett L., author; LeValley, Steve B., advisor; Ames, David R., committee member; Dalsted, Norman L., committee member; Schwab, Clinton R., committee member; Tatum, J. Daryl, committee member; Kimberling, Cleon V., committee memberMeasurements collected during a period of 3.5 years at Tempel Genetics Inc. in Gentryville, IN were analyzed to evaluate the effects of genetic and environmental factors on pregnancy rate using data from 15,375 parity records of two breeds (Landrace and Yorkshire). Female records utilized in the current study ranged from maiden gilts to mature sows through parity 7. All matings were performed via artificial insemination by semen produced within a boar housing facility also operated by Tempel Genetics. Semen was collected, processed, and evaluated on the farm and was not frozen. Pregnancy rate (measured as probability of pregnancy at 21 days post breeding via ultra-sound) of the females was significantly affected by number of services (P<0.05), season of insemination (P<0.05) and parity category (P<0.05). Interactions of (season by number of services and parity by number of services) were also evaluated. Boar age (P<0.05) and days from collection to insemination (P<0.05) were also significant sources of variation for pregnancy rate, while breed did not significantly affect pregnancy rate. The highest pregnancy rate (94.29%) was observed in sows of the parity category 3-4 that were inseminated with three services and using semen from boars less than 5 years of age. Potential opportunities to optimize these three factors should be evaluated by producers who expect to attain maximum pregnancy rate of sows inseminated using fresh boar semen. A model was also developed in Microsoft Excel format using results from the aforementioned analysis as a tool to assist swine producers in evaluating various management options to enhance pregnancy rate. With the use of this model, smaller producers who do not have access to large amounts of internal data can evaluate the potential impact of implementing different management options evaluated within a typical commercial-based swine enterprise.Item Open Access Oropharyngeal bacteria, with respect to animal health classification, and viral serology of Montana bighorn sheep (Ovis canadensis) and domestic (Ovis aries) near to and distant from the wildlife/domestic animal interface(Colorado State University. Libraries, 2010) Miller, David Steven, author; Campbell, Terry W., advisor; Garry, Franklyn, advisor; Chapman, Phillip L., committee member; Kimberling, Cleon V., committee member; Rhyan, Jack C., committee memberRespiratory disease outbreaks attributed to pasteurellosis have lead to conflict at the wildlife/domestic interface, where domestic sheep have been hypothesized to be a reservoir of Pasteuerellaceae strains that cause disease in bighorn sheep. This dissertation compares bighorn sheep ( Ovis canadensis) and domestic sheep ( O. aries) oropharyngeal Pasteurellaceae biovariants from animals classified as diseased and healthy. It also compares bacteriology and viral serology of populations of these species near to and distant from the wildlife/domestic livestock interface. A retrospective study of clinical submissions (1990 - 2004) indicated that 94 Pasteurellaceae biovariants have been associated with domestic sheep classified as diseased. A second retrospective study (1989 - 2004) indicated that 37 Pasteurellaceae biovariants have been associated with bighorn sheep classified as diseased. A prospective study of domestic and bighorn sheep near to and distant from the wildlife/domestic interface indicated that Pasteurellaceae biovariants commonly associated with disease in the retrospective studies were also common in healthy animals, and that there was extensive interspecific sharing of biovariants. This suggests that a simple agent/disease relationship may not exist for Pasteurellaceae in these host species. In addition, it is not clear that either species serves as a reservoir for Pasteurellaceae that are pathogenic for the sympatric species. However, unstated assumptions that single samples represent an animal's Pasteurellaceae microflora are questionable, based on the minimal concordance of biovariants of individual domestic livestock (n = 118) sampled six months apart. Based on the populations in the prospective study, bighorn sheep populations were naive to Mycoplasma, and both Ovis species were largely naive to infectious bovine rhinotracheitis and bovine virus diarrhea 1 and 2. This suggests that these agents may cause outbreaks if introduced into these populations. Cluster analysis of Pasteurellaceae and viral serology results identified four different clusters (P < 0.0001), but these did not closely correspond to species and location categories. The results from this study suggest that emphasis on single determinants for causes of respiratory disease outbreaks in domestic and bighorn sheep, rather than determination of risk factors for multiple determinants, may not provide results that are useful for managing disease in these species.