Blood polymorphonuclear neutrophil leukocytes (PMNL), by phagocytosis and reduction, convert NET in indissoluble formazan. Therefore, it is possible to evaluate a metabolic activity of these cells (superoxide production) quantifying, microscopically, this reduction. Seven blood samples were collected from ten Comisana ewes a week before lambing until the third month of lactation. NBT reduction test, either spontaneous or stimulated by bacterial extract, was carried out. The percentages of spontaneous or stimulated reducing PMNL were respectively 15,4% and 41,1%. Analysis of the data showed a higher PMNL's reduction capacity during peripartum.