Dynamics of hematological parameters in female lambs during the first four months of life

Abstract

Important physiological changes affect the blood profile of ruminants during the growth phase, but few studies approach the factors involved in these dynamics in lambs. The aim of this study was to characterize the dynamics of hematological parameters, of total plasma protein (TPP), and of fibrinogen in healthy female lambs during the first four months of life. Blood samples of 35 female lambs were collected at 30, 60, 90, and 120 days old to perform the complete blood count (CBC). The erythrocyte and leukocyte parameters, TPP, and fibrinogen were determined. The means for total red blood cell (RBC) counts at 60 and 120 days differed (P < 0.05) from the initial mean, showing a peak of 13.6 x 106 cells µL-1 at 60 days old. The mean values for packed cell volume (PCV) and hemoglobin (Hgb) concentration increased (P < 0.05) until 90 days and decreased at 120 days (36.6% to 33.7% and 11.4 g dL-1 to 10.6 g dL-1 between 90 and 120 days, respectively). The means for mean corpuscular volume (MCV) and for mean corpuscular hemoglobin concentration (MCHC) increased (P < 0.05) between 30 and 120 days (27.5 µm3 to 29.7 µm3 and 26.6% to 31.4%, respectively). The total white blood cell (WBC) count increased (P < 0.05) and reached a peak at 90 days (9,314 cells µL-1). The peaks for segmented neutrophils (5,141 cells µL-1) and lymphocyte counts (4,236 cells µL-1) occurred at 60 and 90 days, respectively. The means for neutrophil/lymphocyte ratio were similar (P > 0.05) between the ages (mean of 1.8) but higher than the reference value for adult sheep (0.5). The initial mean for eosinophil counts (2 cells µL-1) was lower (P < 0.05) than all subsequent ones, and the monocyte count showed the lowest level (P < 0.05) at 120 days (232 cells µL-1). The mean for TPP at 60 days (6.4 g dL-1) was higher (P < 0.05) than the other ages. Except for band neutrophil and basophil counts, and fibrinogen concentration, the hematological parameters and the TPP of female lambs are influenced by age until four months of life and differ from the reference intervals established for adult sheep. Therefore, the interpretation of CBCs performed in female lambs should be made on the basis of age group-specific reference intervals.