Theses and Dissertations at Montana State University (MSU)
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Item Prevalence and production impacts of subclinical mastitis in extensively managed ewes(Montana State University - Bozeman, College of Agriculture, 2019) Knuth, Ryan Michael; Chairperson, Graduate Committee: Megan Van Emon; W. C. Stewart, J. B. Taylor, C. J. Yeoman, B. Bisha, M. L. Van Emon and T. W. Murphy were co-authors of the article, 'The prevalence and etiology of subclinical mastitis and association with milk somatic cell count in western range flocks' submitted to the journal 'Journal of animal science' which is contained within this thesis.; W. C. Stewart, J. B. Taylor, C. J. Yeoman, M. L. Van Emon and T. W. Murphy were co-authors of the article, 'Udder morphometry and health and their relationship with ewe somatic cell count and productivity in extensively manged research flocks' submitted to the journal 'Journal of animal science' which is contained within this thesis.Mastitis results from a bacterial infection of the mammary gland and is a devastating disease to all sheep producers from both an economic and animal welfare perspective. Clinically infected ewes display visually apparent symptoms, however, subclinically infected ewes do not although this form is more common. Since milk is a direct commodity of dairy animals, much of the past research has been conducted here and the production and economic impacts of subclinical mastitis are less clear in non-dairy (e.g., meat- and wool-type) ewes. The objectives of the first study were to identify bacteria species present in milk collected from clinically healthy ewes and evaluate somatic cell count (SCC) thresholds relating to intramammary infection. Milk samples were collected from two research flocks in the Western U.S. (Montana State University = MSU; U.S. Sheep Experiment Station = USSES). Bacteria were identified by both culturing and identification via mass spectrometry and polymerase chain reaction methods. Overall, 60 bacteria species were identified using mass spectrometry and the most common belonged to the Bacillus and Staphylococcus genera. The ideal SCC thresholds to predict intramammary infection ranged between 240 x 10 3 to 1370 x 10 3 cells/mL, depending on the flock and time of collection. In the second study, milk samples were collected and udder and teat morphometric traits were observed to predict ewe productivity via dam 120 day adjusted litter weaning weight (LW120). Udder and teat characteristics were assessed on a linear scale at each sampling and included teat length, udder symmetry, and presence of supernumerary teats, to name a few. The effect of log10-transformed SCC (LSCC) on ewe productivity was dependent on lactation stage and production year, but when significant, indicated a 9.2-14.7 kg reduction in LW120 associated with a 1-unit increase in LSCC. Factors which influenced LSCC included parity, production year, and presence of supernumerary teats in USSES ewes and, for MSU ewes, included teat length, external teat damage, udder symmetry, and presence of supernumerary teats. The results indicate subclinical mastitis is common and additional studies investigating techniques to mitigate its severity and prevalence in meat- and wool-type ewes are warranted.Item The pathogenesis of ovine mastitis due to Pasteurella Mastidis(Montana State University - Bozeman, College of Agriculture, 1951) Firehammer, Burton D.Item The dissociation of Pasteurella mastitidis(Montana State University - Bozeman, College of Agriculture, 1947) Matisheck, Peter H.Item The effects of overmilking on the mammary gland and the incidence of mastitis(Montana State University - Bozeman, College of Agriculture, 1963) Quesenberry, Neil C.Item Molecular and functional characterization of bovine C5a receptor(Montana State University - Bozeman, College of Agriculture, 2006) Nemali, Sailasree; Chairperson, Graduate Committee: Mark T. Quinn.Anaphylatoxin C5a is an important chemotactic factor for bovine neutrophils, and is the earliest inflammatory agent formed during bovine mastitis. Bovine neutrophils respond to C5a and its truncated form C5a des arg with similar affinities unlike human neutrophils. Therefore, to test the hypothesis that the bovine C5a receptor structure and signaling differ from that of the human C5a receptor, we cloned and analyzed the bovine C5a receptor. In the present investigation, the bovine C5a receptor encoding cDNA from bovine bone marrow was cloned and the recombinant C5a receptor protein was expressed in CHO-K1 cells. Analysis of predicted C5a receptor amino acid sequence demonstrated 69.1%, 71.3%, 59.4%, 61.6%, and 33.2% identity with that of human, dog, mouse, rat, and trout respectively. The bovine C5a receptor mediated signaling was via pertussis toxin insensitive Gá-protein, and mediated L-selectin shedding on the activated neutrophils. The homologous-, and heterologous desensitization experiments provided further evidence that C5a and C5a des arg could desensitize C5a receptor signaling as well as IL-8 receptor mediated signaling. We further analyzed the expression profiles of the C5a receptor on bovine peripheral blood leukocytes with the receptor-specific antibody and FITC labeled C5a des arg. The monoclonal antibody as well as C5a des arg FITC failed to detect C5a receptor on peripheral blood mononuclear cells. Furthermore, we probed for the expression of C5a receptor gene and protein expression in Mac-T cell line--an immortalized bovine mammary epithelial cell line--, to test the hypothesis that bovine epithelial cells express C5a receptor protein. The results of RT-PCR analysis and FACS analysis for the expression of C5a receptor demonstrated the presence of the C5a receptor in these cells. This investigation led to the elucidation of the structure and function of bovine C5a receptor in neutrophils. The analysis of the C5a receptor expression in peripheral blood leukocytes demonstrated that it was constitutively expressed in neutrophils only. Mac-T, a mammary epithelial cell line expresses C5a receptor. Future studies understanding the function of C5a receptor in these cells will contribute to the knowledge of bovine inflammation.