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Clinical mastitis in dairy cows: studies of bacterial ecology and somatic cell count patterns
Ort / Verlag
ProQuest Dissertations & Theses
Erscheinungsjahr
2003
Link zum Volltext
Quelle
ProQuest Dissertations & Theses A&I
Beschreibungen/Notizen
Patterns of bacterial intramammary isolates and somatic cells counts were studied in dairy cows. A quantitative assessment was made of the relationship between intramammary bacterial isolates during the dry period and clinical mastitis. The probability of a quarter succumbing to clinical mastitis during location increased when a number of different bacterial species were cultured during the dry and post-calving period. There were evidence of synergistic and inhibitory associations between different species of bacteria and evidence of differences in the force of infection between farms and in different months of the year. Patterns of quarter and cow somatic cell counts were investigated in relation to clinical mastitis. Quarters with a somatic cell count in the range 41 - 100,000 cells/ml had the lowest risk of clinical mastitis in the following month. Quarters with a somatic cell count greater than 200,000 cells/ml were at the greatest risk of clinical mastitis in the following month. There was a reduced risk of clinical mastitis between one and three months later in quarters with intermediate somatic cell counts (61,000 - 150, 000 cells/ml) compared with quarters above or below this level. Quarters with intermediate somatic cell counts were most likely to remain in this range over time, and this may partially explain why quarters were at a reduced risk of clinical mastitis for up to three consecutive months. Investigations of patterns of cow somatic cell count over lactation, identified that increased maximum and standard deviation log SCC, rather than increased geometric mean, were the best indicators of clinical mastitis. Increased maximum log SCC was associated with clinical mastitis caused by the pathogen types. Increased standard deviation log SCC was associated with Staph. aureus and Strep. uberis clinical mastitis and increased coefficient of variation log SCC was associated with E. coli clinical mastitis. Increased geometric mean lactation SCC was associated with an increased risk of Staphylococcus aureus clinical mastitis but a reduced risk of E. coli clinical mastitis.