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Browsing by Author "Gould, Daniel H., committee member"

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    Dairy cow mortality
    (Colorado State University. Libraries, 2010) McConnel, Craig Stephen, author; Garry, Franklyn B., advisor; Hill, Ashley E., committee member; Lombard, Jason E., committee member; Gould, Daniel H., committee member
    Dairy cow mortality levels in the United States are excessive and increasing over time. This is both a financial concern and an important animal welfare issue. Summary studies of dairy cow removal have been in the literature for decades although information specifically related to dairy cow mortality has been sparse. Even though the increase in dairy cow mortality has generated concern within the industry, the reality is that there is no standard by which to define what might be considered the 'natural' or 'normal' level of mortality in dairy cow production. No evidence suggests that there is any one thing that has led to the rise in mortality and that could be reversed to lower death rates. Rather, numerous agents (influential persons, places, or things) apparently act in concert to influence specific outcomes that may lead to death. The "agents" intimated to be responsible for increasing mortality have been primarily described through the analysis of associations between mortality levels and descriptors such as days postpartum, parity, herd size, and genetics. Such analyses may provide a means for understanding populations at risk but can only illustrate broad principles related to manageable risk factors, potential mitigation procedures, or specific pathologic outcomes. Other studies have attempted to define individual occurrences of death based on the final outcome. Rather than looking at population levels of diseases and associated levels of death, these studies have focused on the pathophysiologic or anatomic descriptions of specific deaths. Such analyses fail to account for the non-biologic unconstrained inputs such as management and environmental factors that ultimately set a pathologic sequence in motion within an at-risk population. Ultimately, with regard to excessive and increasing dairy mortality the difficulty lies in defining the problem (establishing what distinguishes farms with higher death rates from those with more desirable rates) and locating the problem (finding where the trouble really lies within the complex of causal networks on a dairy). This leads to the problem of identifying the actions that might effectively narrow the gap between what-is and what-ought-to-be. Understanding the complexity within such a system demands the recognition of its evolving ecology. Within this evolving industry there is no legitimate means for resetting practices and outcomes back to some undefined acceptable level. Rather than attempting to reverse the irreversible, it would be wise to instead work within the system to improve outcomes through sound scientific principles. The intention of the following work is to characterize and elucidate such principles in an effort to facilitate best intentions becoming better outcomes.
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    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 member
    Data 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.