Lactose in the blood and urine of cows

Summary Lactose could not be detected in the urine of non-lactating cows but was invariably found, though usually in low concentration, in the urine of lactating cows; the highest values were observed with cows of high lactation number. Towards the end of an extended milking interval of 39 h, the lactose concentration in the blood and the excretion of lactose in urine increased markedly, but on milking there was a rapid return to original values. Lactosuria was observed in pregnant cows from about 20 days before parturition, and at parturition there was a temporary, marked increase in the excretion of lactose in urine.