[Methemoglobinemia in pigs and the effect of nitrites on the health and growth of piglets].

In 357 pigs of ten age categories fed the commercial feed mixtures the highest methemoglobinemia was found in piglets up to three days of age (3.62%) and the lowest in sows and boars (2.25%). In twelve per cent of animals of the whole set the values of methemoglobin (MHb) reached or exceeded 4%, the maximum was 8.1%, without any clinical symptoms. Except the anemic piglets, these values were not observed in sucking piglets older than three days. Testing of the formation and of the subsequent reduction of methemoglobin in vitro by the action of 14.4 micrograms of sodium nitrite in 1 ml of blood proved no increased disposition to methemoglobinemia in new-born piglets. The levels with 29 to 40% of methemoglobin reached their peaks in all age groups within 50 min. The reconversion was the slowest in adult pigs, the quickest in new-born and weaned piglets; after seven hours the reconversion was almost complete. If recalculated to the initial concentration of hemoglobin, its highest transformation to methemoglobin occurred in older and adult pigs, the lowest in the piglets up to the age of six days and at sideropenic anemia. Short-term administration of sodium nitrite to sows prior to delivery resulted in an increased methemoglobin level in new-born piglets, out o of which 12% were still-born. The repeated administration of sodium nitrite to the sucking piglets (33 to 132 mg per day) influenced neither their health condition nor the body weight gains. The effects of nitrates, nitrites and mechanisms of the reconversion of methemoglobin to hemoglobin are discussed.