92. the Lasting Effect of Udder Inflammation on Milk Lactose Content in Dairy Cows

Milk lactose content (LC) reduces with parity in dairy cattle and shows an inverse relation with somatic cell count. The aim of this study was to investigate if the lifetime decrease in LC is due to cumulative number of experienced udder inflammations. For this purpose, milk test-day data of Austrian Fleckvieh cows were available together with records of acute (AM) and chronic mastitis (CM) cases. In addition, inflammations were also defined by using high test-day somatic cell count: ≥200,000 (SCC200) or ≥400,000 cells/ml (SCC400). Inflammation events were calculated for each test-day using data collected across the cows’ lifespan, i.e. across all available lactations. The effect of cumulative inflammations on LC was highly significant, with LC being the highest when 0 mastitis events were experienced and significantly different from LC estimated for test-day records linked to ≥1 event. Findings demonstrate that the lifetime LC decrease can be seen as a mammary memory indicator and represents the combined result of physiological aging and past inflammations.