Hematological and biochemical findings in pregnant, postfoaling, and lactating jennies

The aims of this study were to (1) verify if significant changes occur in hematological and biochemical parameters in jennies during the last 2 months of pregnancy and the first 2 months of lactation, and (2) determine any differences with mares. Hematological and biochemical parameters were evaluated in jennies every 15 days during late pregnancy, parturition, and early lactation. The Kolmogorov-Smirnov test, analysis of variance for repeated measurements and Tukey's multiple comparison test as post hoc were applied. The significance level was set at P < 0.05. Statistical analysis showed differences related to time for Red Blood Cells (RBC) count and Hematocrit (HCT), White Blood Cells (WBC) count, platelet count (PLT), total proteins, blood urea, triglycerides and total cholesterol concentrations, aspartate aminotransferase, gamma-glutamyltransferase, creatine-phosphokinase activities, sodium (Na) and potassium (K). RBC and HCT were higher in late pregnancy than at foaling and during lactation. The relative anemia might be due to increased water ingestion because of fluid losses. The WBC count was higher at foaling than during late pregnancy and lactation. This could be related to the release of cortisol and catecholamine during delivery. The PLT trend showed lower values from delivery to the first 2 months of lactation compared to late gestation. Blood urea increased near parturition, and then remained constant during delivery and lactation, which might be due to the high energy demand at the beginning of lactation. Triglycerides and total cholesterol showed a decrease from delivery through the lactation period. Thus, jennies seem to have a similar metabolism of fats to ponies and draft horse mares, characterized by a greater fat content and mobilization than light breed horses. Aspartate aminotransferase activity decreased at parturition and early lactation, probably because of a predominance of anabolic over catabolic processes during pregnancy. Gamma-glutamyltransferase activity was lower at delivery and during lactation than at late gestation. This could be due to a physiological load on the liver in the perinatal period. Gamma-glutamyltransferase activity was always higher than in mares, but within the normal range for adult donkeys. Creatine-phosphokinase decreased near delivery, then was constant from parturition through the first 2 months of lactation. Na decreased during lactation, probably due to an increased renal retention mediated by aldosterone release during pregnancy. K showed the same trend as Na, and concentrations are in line with the species. The higher K during pregnancy may be due to reabsorption by the gut. Total proteins decreased more during the postpartum period and lactation than in the gestational period. In conclusion, our results showed significant changes in hematological and biochemical parameters in jennies during the last 2 months of pregnancy and the first 2 months of lactation and these changes are only partially comparable to mares.