Decrease of the lactose concentration in cows milk as a result of increased permeability of the tissue barriers between milk ducts and blood

Published data on lactose concentrations in milk and urine of cows indicate, that both the decrease of this genuine product of the mammary secretory cells in the milk and its appearance in urine are connected with mastitis, severe general diseases (fever, anorexia), prolonged milking intervals, application of high doses of oxytocin, drying off and onset of lactation at parturition. The lactose transfer from the milk into blood and urine occurs predominantly during the storage of the milk within the alveolar lumina, milk ducts and cisterns. Own results show, that the extent of the changes of the lactose concentration in milk and urine reflects the severity of mastitis, the degree of medicamental udder iritation, the method of drying off and physiological structural changes of the mammary tissue. Lactose values in urine of below 0,5 g/l characterize good udder health and regular udder evacuation. At parturition, around day 3 after drying off and at the beginning of an acute mastitis peak values of more than 4g lactose per liter urine can be expected. The urinary lactose content reflects the state of integrity of the tissue barriers (tight junctions of mamary epithelia) between milk and blood.