Silanikove, N., Biology of Lactation Laboratory, Institute of Animal Science, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Rauch-Cohen, A., Biology of Lactation Laboratory, Institute of Animal Science, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Shapiro, F., Biology of Lactation Laboratory, Institute of Animal Science, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Arieli, A., Department of Animal Science, Faculty of Agricultural, Food and Environmental Sciences, Hebrew University of Jerusalem, Rehovot 76-100, Israel
Merin, U., Food Quality and Safety, Institute of Postharvest and Food Sciences, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Leitner, G., National Mastitis Reference Center, Kimron Veterinary Institute, Ministry of Agriculture and Rural Development, P.O. Box 12, Bet Dagan 50250, Israel

The aim of this work was to study the effects of mastitis induced by intramammary lipopolysaccharide (LPS) challenge on milk oxidative stability, as well as to understand the underlying biochemical processes that cause such changes. LPS challenge was associated with nitric oxide burst from the surrounding mammary epithelial cells and consequently induced nitrosative stress that was induced by the formation of NO2• from nitrite by lactoperoxidase. This response was associated with an ∼3-fold increased formation of hazardous compounds: nitrotyrosines, carbonyls and lipid peroxides. We sustained the involvement of xanthine oxidase as a major source of hydrogen peroxide. In consistent with previous findings, catalase has been shown to play a major role in modulating the nitrosative stress by oxidizing nitrite to nitrate. The current hygienic quality criteria cannot detect mixing of low-quality milk, such as milk with high somatic cells, and nitrite with high-quality milk. Thus, development of an improved quality control methodology may be important for the production of high-quality milk. © The Animal Consortium 2011.