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 autoxidative behavior of milk lipid fractions in systems of controlled composition(Montana State University - Bozeman, College of Agriculture, 1966) Ku, ShunItem Study of intracellular proteinases of some bacteria(Montana State University - Bozeman, College of Agriculture, 1962) Vadehra, Dharam Vir; Chairperson, Graduate Committee: J. C. Boyd.Item An economic study of milk produced and processed for manufacturing purposes in selected Montana areas(Montana State University - Bozeman, College of Agriculture, 1968) Cothern, James HaroldItem An analysis of factors affecting the demand for milk in Montana(Montana State University - Bozeman, College of Agriculture, 1980) Barkell, John ElliottItem The effects of proteins from skim milk and other sources on tomatoes(Montana State University - Bozeman, College of Letters & Science, 1951) Dawson, Frederick C.Item Marketing fluid milk in Montana(Montana State University - Bozeman, College of Agriculture, 1952) Clark, Ralph WaldoItem The development of a hypothetical federal milk marketing order for the Great Falls-Hi-Line Area and a comparison of this order with the Montana Milk Control Law in its present state of effectiveness(Montana State University - Bozeman, College of Agriculture, 1963) Litschauer, John George; Montana. Milk Control BureauItem The development of a milk pricing formula at the processor-distributor level for Montana(Montana State University - Bozeman, College of Agriculture, 1966) Vesterby, Marlow ClaytonItem The kind and number of bacteria found in colostrum obtained by milking cows before and after parturition(Montana State University - Bozeman, College of Agriculture, 1950) Lofthouse,Thomas F.