Thesis defense Yvette de Geus

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The bulk milk total bacterial count (BTBC) is essential for milk quality, as a high bacterial load shortens shelf life and negatively affects dairy processing. Therefore, Dutch dairy processors maintain a maximum TBC of 100,000 colony-forming units per ml of bulk milk. If this limit is exceeded, goat farmers receive milk price penalties.

Identifying the causes of an increased bacterial count makes it possible to take targeted preventive measures to control the BMTBC. We found three main sources for BMTBC. First, bacteria can be derived from the milking equipment and/or environmental bacteria present on the udder can be milked into the bulk. Secondly, individual goats with mastitis can excrete high numbers of bacteria into the milk. Thirdly, a high bacterial count is found around kidding with the flow cytometer. However, additional bacteriological tests do not show these high bacterial counts around kidding. Possibly, the measurement of the bacterial count with the flow cytometer is disturbed by a simultaneous increase in both the cell count and the bacterial count in milk from animals at the end of lactation, which may indicate a measurement error.

Preventive measures to reduce the BMTBC are: optimalisation of hygiene of the milking equipment, and the milking procedure, early identification of goats with mastitis and excluding their milk from the production chain, drying off pregnant goats before kidding and improvement of general udder health.