A literature review; Mastitis, its forms, causative agents, predisposing factors and treatments

Abstract

The season is an important predisposing factor for intramammary infections such as mastitis to occur, and may play an important role in influencing the frequency of udder health issues in a herd scale. The aim of this study was to determine how much of an effect the season had on the average monthly SCC recorded in three dairy herds, known in this study as Farm A, Farm B and Farm C. These three dairy herds are all located in the eastern Republic of Ireland, and would have experienced the same climatic conditions in the period of study, and are assumed to have the same practices performed as regards to milk recording, housing and grazing. The animal husbandry system in Ireland is based on keeping the animals on pasture for the majority of the year, until the winter when the conditions will no longer allow for grazing. This gives a clear separation between the winter housing period and the rest of the year. The expected trend in the data analysed was the increase of herd average SCC during housing, with lower numbers seen in the spring and summer. The data was analysed by calculating the average SCC of the herd on a monthly basis for each of the three farms. In addition, the median values were also found. From this data, it was possible to discern the trends in the data throughout the period of milk recording for each of the three farms. Significantly elevated individual milk recording results had the effect of driving up the herd average SCC, which could potentially give an erroneous impression of the true overall udder health situation in each herd. Therefore, in addition to the average SCC measurements, an average was calculated for each herd where significantly high scoring cows were omitted from the analysed data. The threshold set for this study was 1 million somatic cells/ml milk. The data before exclusion of high scoring cows gave no indication of there being an increased propensity for subclinical or clinical mastitis in winter, in fact the highest cell counts were in some cases found in the summer. After exclusion, the data set indicated a situation more closely resembling the expected seasonal influence, where the period of housing recorded the highest SCC numbers below 1 million cells/ml. The significance of these findings however was deemed to be insufficient to provide evidence for conclusion that the incidence of mastitis is higher in the winter season in the Irish system. There is however enough evidence to suggest that the season will have a significant influence on the herd SCC, where the summer period will have more cases of exceedingly high scoring cows.