High levels of nitrate once metabolized to nitrite can interfere with the oxygen-carrying capacity of hemoglobin, resulting in increased methemoglobin and, subsequently, methemoglobinemia (MetHb) if the animal is deprived of significant amounts of oxygen; however, the level of nitrate exposure necessary to induce MetHb in sows is not clearly defined. The gene discussed is HBG2; the disease is methemoglobinemia.