Factors associated with intra-mammary infections dynamic and development of tailored sampling strategies and analytical methods.

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Mastitis, an inflammation of the mammary gland most often resulting from a bacterial infection, is a multi-faceted disease and is one of the most expensive dairy cow health problems. The estimated cost of mastitis for Canadian dairy producers is approximately $300 million per year. Mastitis reduces milk yield of dairy cows and affects animal welfare with clearly visible and measurable signs of sickness and discomfort. Furthermore, antibiotics treatments used to treat and prevent mastitis represent a very large proportion of the antibiotics used on Canadian dairies and constitute a risk of residues in the milk supply that could be a threat for public health. Finally, there is currently no gold standard test to diagnose intramammary infections (IMI) and this later aspect has important repercussions both in research and in practice. The long term objectives of the current research program are to further improve our understanding of mastitis pathogens epidemiology and to develop novel tools for monitoring IMI dynamic on dairies. We first propose to quantitatively evaluate the effect of different sampling protocols on the validity of the results commonly presented in udder health research. This first objective will allow the definition of clear sampling strategy guidelines for longitudinal udder health research, an aspect that is currently cruelly missing to the mastitis scientific community. Novel analytical methods will then be developed and proposed to control potential remaining biases and improve the validity and comparability of udder health research results. The general principles highlighted in this part of the research program should also be very useful for research in various health disciplines. Secondly, research will be conducted to further extend our understanding of mastitis pathogens epidemiology. As a first step, research on risk factors associated with recurrence of clinical mastitis will be conducted. Results from this study will generate the fundamental knowledge needed to better control mastitis on dairies and will have a profound impact on the Canadian dairy industry by mitigating the important costs associated with mastitis, by improving welfare of dairy cows, and by reducing the use of antibiotics.