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The role of intramammary masses on the transmission and persistence of mastitis-associated pathogens, flock prevalence and the live weight of lambs
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Bamford, Kate Emily (2021) The role of intramammary masses on the transmission and persistence of mastitis-associated pathogens, flock prevalence and the live weight of lambs. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3678232~S15
Abstract
Mastitis is endemic in suckler sheep flocks in the UK and has major implications for farm sustainability and sheep health and welfare. This study aimed to investigate intramammary masses (IMM), their association with acute mastitis and their role in transmission pathways of mastitis-associated pathogens. Ewes with IMM were separated to investigate the success of separation in reducing IMM prevalence and the effect of IMM on lamb growth rates was investigated.
Previous studies have identified a strong association between IMM and acute mastitis and hypothesised that ewes with IMM provide a reservoir of mastitis-associated pathogens.
A 12-month longitudinal study of 570 ewes was carried out. New and reoccurring IMM were recorded each month and ewes with IMM were separated from ewes with no IMM. Somatic cell counts (SCC) and udder conformation investigated at shortly after lambing. Ewes remained separate throughout the study and their lambs were weighed at birth and at regular periods until slaughter. Milk samples were collected during a second two-year longitudinal case-control study and cultured aerobically. Morphologically unique isolates were selected and identified using Matrix-assisted laser desorption ionization time-of-flight (MALDI-ToF MS). Whole genome sequencing (WGS) was carried out on a subset of Staphylococcus aureus samples for molecular epidemiological analysis.
Separating ewes with IMM did not reduce the number of new IMM identified in the flock, indicating that culling will not successfully reduce IMM risk in a flock. SCC were significantly higher in ewes with acute mastitis or intramammary masses than ewes with no mastitis. In the second study, S. aureus was significantly associated with IMM and acute mastitis compared to healthy ewes. WGS analysis evidenced transmission of strains within a flock and persistence within the mammary gland. Lambs of ewes with IMM or acute mastitis had significantly lower growth rates compared to healthy ewes all the way until slaughter, significantly increasing the age at slaughter.
| Item Type: | Thesis (PhD) | ||||
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| Subjects: | Q Science > QR Microbiology S Agriculture > SF Animal culture |
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| Library of Congress Subject Headings (LCSH): | Mastitis, Mammary glands -- Diseases, Udder -- Diseases, Sheep -- Diseases, Staphylococcus aureus | ||||
| Official Date: | May 2021 | ||||
| Dates: |
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| Institution: | University of Warwick | ||||
| Theses Department: | School of Life Sciences | ||||
| Thesis Type: | PhD | ||||
| Publication Status: | Unpublished | ||||
| Supervisor(s)/Advisor: | Green, Laura E. ; Purdy, Kevin J. | ||||
| Sponsors: | Biotechnology and Biological Sciences Research Council (Great Britain) ; Great Britain. Agriculture and Horticulture Development Board | ||||
| Format of File: | |||||
| Extent: | xii, 142 leaves : illustrations (some colour) | ||||
| Language: | eng |
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