Silanikove, N., Biology of Lactation Laboratory, Institute of Animal Science, The Volcani Center, POB 6, Bet Dagan 50250, Israel
Rauch-Cohen, A., Biology of Lactation Laboratory, Institute of Animal Science, The Volcani Center, POB 6, Bet Dagan 50250, Israel
Shapiro, F., Biology of Lactation Laboratory, Institute of Animal Science, The Volcani Center, POB 6, Bet Dagan 50250, Israel
Blum, S., Kimaron Veterinary Institute, National Mastitis Center, POB 12, 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
Leitner, G., Kimaron Veterinary Institute, National Mastitis Center, POB 12, Bet Dagan 50250, Israel

Support of milk production in modern dairy cows demands a large proportion of its own metabolic resources, such as glucose, which might be required under stressful situations. The aim of the experiment was to test the hypothesis that acute immune stress shifts oxidative metabolism to glycolysis. Two mammary quarters in 6 Holstein cows were infused with lipopolysaccharide (LPS), whereas the 2 counter quarters served as controls to the treatment. An additional 6 cows were infused with saline and served as running controls. The LPS challenge induced dramatic transient increases in milk lactate (75-fold) and malate (11-fold) concentrations (both markers of glycolysis) at 24. h posttreatment. No significant changes in lactate and malate concentrations were recorded in control quarters and control animals, indicating that the effect of LPS was restricted to the treated gland. The LPS challenge induced a dramatic transient decrease in milk yield, and lactose and citrate (a marker of mitochondrial metabolism) secretion at 24. h posttreatment. The kinetics were inversely proportional to those of lactate and malate concentrations. Thus, our data suggest that LPS challenge induces acute conversion of epithelial cell metabolism from principally mitochondrial-oxidative to principally cytosolic (glycolytic), which allows the diversion of metabolic resources normally used to synthesize milk to support the immune system. An in vitro bacterial growth test showed that concentrations of lactate, malate, and lactose equivalent to those found in the in vivo experiment delayed and reduced the growth of a pathogenic Escherichia coli strain, suggesting that they play a role in diminution of bacterial multiplication in the mammary gland. © 2011 American Dairy Science Association.