ABSTRACT - The electrolyte and biochemical variables were evaluated in 8 healthy mares, aged 4-10
years. Blood samples were taken after the 8th month of gestation, and then, every 30 days, for 3 consecutive
months. During the lactation, blood samples were taken in the day 7, 15, 30 post partum. Mares were bled
from the jugular vein between 7:30-9:00 AM. The purpose of this study was to determine which
physiological changes occur in serum clinical biochemical analytes in pregnant and lactating mares and to
determine whether the changes between pregnancy and lactation conditions are significant. Two way RMANOVA
showed significant effects of lactation on the changes of all electrolytes and hematochemical
variables, with higher levels of Na+, Pi and urea, and lower levels of Na+, Ca++, K+, creatinine, bilirubin and
triglycerides in lactation than in pregnancy