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    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.
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    The temporal relationship of the ovary and ovarian morphology for the onset and duratin of behavioral estrus in prostaglandin F 2 alpha-treated ewes
    (Montana State University - Bozeman, College of Agriculture, 1984) Courtney, Lynn Patricia; Chairperson, Graduate Committee: James G. Berardinelli
    The objective of this study was to determine the temporal relationship of ovarian follicles and corpora lutea (CL) on the time to onset (TO) and duration (D) of behavioral estrus in PGF 2 alpha- treated ewes. Forty normally cycling Western White-Faced ewes were randomly assigned to one of eight treatments to be either sham-operated (SO) or ovariectomized (OVX) at 36, 44, 52 or 60 h after a PGF 2 alpha injection given on day 12 of the estrous cycle. At the time of injection (Oh) and every 4 h afterwards for 96 h, each ewe was observed for estrus using a teaser ram. At surgery, ovaries of each ewe were macroscopically examined for number and size (mm) of antral follicles and CL. Ovaries of OVX ewes were prepared for histological evaluation. Actual size and number of follicles and CL were determined by taking photographic slides of stained tissue sections and projecting them onto a paper screen. Follicles were classified as atretic (A) or non atretic (NA), and CL as normal or regressing. Proportion of ewes in estrus was lower (P<.05) for OVX ewes (11 of 20; 55%) than for SO (20 of 20; 100%) and there was a time by treatment interaction (P<.05). Mean TO of estrus was 48.2 + or - 3.6 h for OVX ewes which showed estrus and 52.2 + or - 2.4 h for SO ewes (P>.05); and the overall mean was 50.7 + or - 1.9 h. Duration of estrus was 25.6 + or - .8 h for OVX ewes which showed estrus and 32.6 + or - 3.2 h for SO ewes (P>.05); and the overall mean was 29.8 + or - 2.5 h. There were no treatment effects for either TO or D of estrus (P>.05). At 44, 52 and 60 h fhe number of actual large NA (LNA) follicles was negatively associated with TO of estrus (r= -.97, -.73, -.87, respectively) and positively associated with D of estrus (r-.76, .70, .65). Actual CL volume was positively associated with D of estrus (r=.84, .58, .68) and negatively associated with TO of estrus (r= -.93, -.36, -.39). Total number of actual antral follicles did not change over time (P>.05), nor did number of follicles in the small (1-3.9mm), medium (4.0-5.9mm) and large (>6.0mm) size groups (P>.05). There was a shift in class of follicles such that number of medium NA follicles decreased and number of LNA follicles increased from 36 to 52 h (PC.05). CL size was smaller at 60 h (P<.05), while CL volume remained constant (P>.05). These results indicated that there is a temporal relationship of the ovary for the TO and D of estrus in that the ovary is required for at least 44 h, probably longer, for estrus to occur. However, once estrus has been initiated the presence of the ovary is no longer required for the normal expression of estrus. Individual variation in the TO and D of estrus may be related to differences in the number of LNA follicles and (or) CL volume.
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    Studies on fecal analyses for determining forage species and protein in the diet of range ewes
    (Montana State University - Bozeman, College of Agriculture, 1951) McKinney, Mark
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    Influence of supplementation on the productivity of ewes grazing improved pasture and suckling twins
    (Montana State University - Bozeman, College of Agriculture, 1988) Frey, Ana Lidia
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    Factors affecting ovulation rate, fertilization rate and ova normality in ewes managed under range conditions
    (Montana State University - Bozeman, College of Agriculture, 1965) Engle, Clair C.
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    Induced lactation in non-pregnant ewes
    (Montana State University - Bozeman, College of Agriculture, 1958) Bellows, Robert A.
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    Gross and histometric characteristics of oviducts and uteri and the effects of estrogen during the puberal transition in ewe lambs
    (Montana State University - Bozeman, College of Agriculture, 1990) Lewis, Andrew Wade
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    Effect of excess degradable intake protein on ovarian steroids, oviductal proteins and early embryonic development in ewes
    (Montana State University - Bozeman, College of Agriculture, 1998) Weng, Jie
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    The effects of pre-breeding and post-breeding feed treatments on reproductive phenomena of ewes managed under range conditions
    (Montana State University - Bozeman, College of Agriculture, 1959) Hoxsey, Victor L.
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    Influence of energy or protein supplementation on forage intake of pregnant ewes grazing Montana winter range
    (Montana State University - Bozeman, College of Agriculture, 1993) Soder, Kathy Jo
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