Browsing by Subject "Mastitis"

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    Efficacy of on-farm programs for the diagnosis and selective treatment of clinical and subclinical mastitis in dairy cattle.
    (2009-08) Lago Vázquez, José Alfonso
    The research reported in this dissertation includes two multi-state multi-herd clinical trials evaluating the efficacy of on-farm programs for the diagnosis and selective treatment of clinical and subclinical mastitis in dairy cattle. The use of an OFC system for the selective treatment of clinical mastitis during lactation reduced intramammary antibiotic use by half and tended to reduce withholding time by one day, without significant differences in days to clinical cure, bacteriological cure risk, new infection risk and ICR risk (where the ICR risk represented the presence of infection risk, clinical mastitis risk, or removal from herd risk) within 21 days after the clinical mastitis event. Similarly, there were no differences between both treatment programs in long-term outcomes such as recurrence of clinical mastitis in the same quarter, somatic cell count, milk production, and cow survival for the rest of the lactation after the clinical mastitis event. The treatment with intramammary Cephapirin Sodium of cows and quarters based on CMT results alone, or sequential testing using OFC to diagnose Gram-positives in CMT-positive quarters resulted in a higher bacteriological cure risk and reduced the ICR risk within 21 days after enrollment (significantly and only numerically, respectively for treatment each program). The implementation of both treatment programs required the administration of intramammary treatment and extended the time that milk is withhold from the market. Both programs resulted in a significantly lower clinical mastitis risk and lower milk SCC during lactation (significantly and only numerically, respectively for each treatment program). However, the implementation of both treatment programs did not result in higher milk production, improved reproductive performance or lower risk for removal from the herd. A secondary objective of both clinical trials was to validate the use of the Minnesota Easy Culture Bi-Plate System. This OFC system is a useful cow-side test to correctly identify bacterial growth, Gram-positive bacterial growth, or Gram-negative bacterial growth in quarter secretion samples from clinical mastitis cases and in CMT-positive quarter milk samples collected after parturition. Treatment decisions based on identification of bacterial growth, or Gram-positive bacterial growth specifically, were correct over 73% of the time.
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    Evaluation Of Selective Dry Cow Therapy For Controlling Mastitis And Improving Antibiotic Stewardship In U.S. Dairy Herds
    (2020-03) Rowe, Samuel
    The objective of this research was to identify strategies that reduce antibiotic use at dry-off (dry cow therapy; DCT) without having negative effects on cow health and productivity. Chapter 2 reports findings from a cross-sectional study of 2,889 late lactation cows from 80 herds in the US. Herds were purposively selected to achieve near-equal representation of four bedding materials of interest. Each herd was visited twice. At each visit, aseptic quarter-milk samples were collected (n = 10,448), along with bedding samples (n = 158). Milk and bedding samples were cultured under aerobic conditions. Quarter-level prevalence of IMI was 21.1%, indicating that selective DCT (SDCT) could result in a more efficient use of antibiotics than blanket DCT (BDCT) in some U.S. herds. Counts in bacteria were positively associated with IMI, indicating that antibiotic use at dry-off could potentially be reduced by preventing IMI during lactation through improved bedding management. Chapters 3-5 report findings from a multi-site, randomized, controlled, clinical trial. Cows (n=1275) from 7 herds at 4 sites were randomized to either BDCT, rapid culture-guided SDCT or algorithm-guided SDCT. Health and productivity were monitored during the dry period and the first 120 days of lactation. Both SDCT approaches reduced antibiotic use at dry-off by 55%. Both SDCT approaches performed similarly to BDCT for dry period IMI dynamics (IMI cure, new IMI and post-calving IMI risk; Chapter 3) and post-calving health and production (clinical mastitis and culling/death rates, somatic cell counts and milk yield; Chapter 4). The agreement (Cohen’s Kappa; κ) and negative predictive values (NPV) for detection of IMI, as determined by the reference test, laboratory-based aerobic culture were rapid-culture (κ = 0.28 , NPV = 0.87) and algorithm (κ = 0.09, NPV = 0.80), indicating that some infected quarters escaped antibiotic treatment at dry-off (Chapter 5). Culture- and algorithm-guided SDCT can be used in commercial dairy farms for reduction of antibiotic use.
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    Radio News Briefs for a Growing Minnesota, November 22, 1968
    (University of Minnesota, Agricultural Extension Service, 1968-11-22) University of Minnesota, Agricultural Extension Service