[Dynamics of methemoglobin levels in the blood of calves in relation to the ingested quantity of nitrates and the transrenal transport of nitrates].
Changes of methaemoglobin levels were investigated in the blood of suckling calves. Transrenal passage of nitrates was determined in dependence on the ingested amount of nitrates. The experiments were conducted under defined husbandry conditions; no excessive nitrate and nitrite supplementation of the calves by feeds and water could be stated. Imitation of possible field conditions when mainly water, but feeds too, may contain higher nitrate and nitrite levels, was carried out by peroral administration of an aquaeous solution of KNO3 to calves. The administered dose was increased from one to 2, 5 and 10 g per animal and day, respectively, in weekly intervals. MtHb determination in the blood of experimental calves on day 1 and 5 of the administration of 1 g KNO3 revealed no significant values. On day 1 and 5 of the administration of 2, 5 and 10 g KNO3 per animal and day, respectively, a significant increase of MtHb levels in the blood of calves was observed 2 and 3 hours after administration, followed by a decrease 4 hours after administration. The maximum values of MtHb in the blood of experimental calves, observed 3 hours following application of the respective KNO3 dose, were within the tolerance limits of the reference values. In urine, 3 hours after the administration of 10 g of KNO3 a mean nitrate value of 941.40.