Mastitis Resistance to Enhance Dairy Food Safety

NON-TECHNICAL SUMMARY: Milk is a highly nutritious food that can harbor a variety of microorganisms and be a source of foodborne pathogens. Milk quality includes both microbiological characteristics and SCC of bulk tank milk and can be influenced by environment, milking practices and udder hygiene. Regulatory limits for bulk milk are based on determination of total bacterial counts of 4 milk samples in each 6 month period but as herd size has increased, processors are increasingly performing microbial counts on each load of milk. When bulk tank loads of milk are routinely tested, there is considerable variation in microbial counts. Surveys of the bacteria present on cows' udders when they enter the milking parlor have indicated that certain housing practices increase the level of thermoduric and spore forming bacteria on udder skin. Investigations have also been done to use newer, faster methods of microbial detection that may improve the response time from several days to less than one day. This rapid response time would greatly reduce the penetration of contaminated milk into the processing stream and reduce risks to rural inhabitants that choose to consume raw milk. Bacterial quality of milk is a major reason for concern among leading dairy processors is the bacterial quality of their milk and they are increasingly linking payments for milk to microbial quality. The ability to achieve processor goals for microbial quality requires an understanding of the management factors that influence these counts. Integration of research outcomes and extension programming. This project will allow us to develop practical methods to quickly measure, diagnose and solve bacterial milk quality problems. Interventions identified in this project will be quickly integrated into Extension Dairy team programming and our existing dairy websites. We expect to identify key management practices associated with microbial quality of bulk tank milk, determine associations between the occurrence of spikes in coliform counts and the occurrence of Salmonella & Listeria spp. in raw milk, and develop monitoring techniques and best management practices that will result in reduced microbial loads in raw milk. <P>
APPROACH: The objective of this project is to develop and evaluate new technologies that can be used to advance milk quality and dairy food safety. We will identify key management practices associated with microbial quality of bulk tank milk, determine associations between the occurrence of spikes in coliform counts and the occurrence of Salmonella & Listeria spp. in raw milk, and develop monitoring techniques and best management practices that will result in reduced microbial loads in raw milk. Data for this project will be obtained from 10 commercial dairy farms that ship full tankers of milk to a single processor. Microbial quality of samples of bulk tank milk will be assessed using bacterial count data (standard plate count; laboratory pasteurized count, coliform counts) and somatic cell count data performed on each load of bulk tank milk by the milk processor. Microbial quality will also be measured by detection of specific zoonotic pathogens isolated from milk samples and studies will be performed to determine if the quantity of coliform bacteria in milk can be used to predict the occurrence of Salmonella spp. and Listeria spp. in bulk milk. Study personnel will visit the farms for a 10 week intensive monitoring period to collect data to assess the relationship between measures of milking performance and the occurrence of coliform bacteria in milk. Practical methods to monitor likely causes of microbial contamination will be evaluated. The monitoring technologies developed in this study will be rapidly transferred to dairy farms in training programs that will be developed for dairy professionals.