Hematologic responses to shearing stress in pregnant Ile de France ewes with low and high basal hematocrit levels
Penka Moneva, Marina Tsaneva, Nikola Metodiev, Ivan Yanchev and DimitarGudev
Abstract: The object of the present study was to investigate some hematological responses to shearing stress. Thirty Ile De France ewes were selected from an experimental herd according to their hematocrit level and were allocated into 3 groups as follows: low hematocrit (LHct) group (hematocrit range 19.7-27.9%), high hematocrit (HHct) group (hematocrit range 32.0-36.9%) and mean hematocrit (MHct) group (hematocrit range 28.3-29.8%). The traits investigated were lactate and hematological indices.The experiment was conducted at the end of the first month after artificial insemination. Daily minimum and maximum ambient temperatures during the whole experimental period were 13.4 and 24.2°C, respectively. Blood samples were taken by jugular venipuncture before shearing, immediately after shearing, at 3h and 24h after shearing.
Shearing resulted in an increase in blood values of red blood cells, hemoglobin and hematocrit as well as a decrease in plasma volume in all ewes. Nucleated red blood cells (NRBCs) count and mean corpuscular hemoglobin concentration (MCHC) declined significantly in LHct ewes only. Low hematocrit ewes had higher percent of hematocrit (P > 0.05) and lactate (P > 0.05) increase in response to shearing, compared to HHct ewes. All blood parameters returned to normal values at 3 h after shearing.There was a significant correlation between the rates of NRBC and plasma volume decline (r = -0.66779) in response to shearing. Blood lactate levels increased in HHct and MHct ewes at 48 h after shearing compared to the respective levels at 3 h after shearing.
The data reported herein suggests that LHct ewes, unlike HHct ewes have higher capacity to cope with acute stress-induced increase in oxygen and energy demand. Also, adaptation to a lack of skin insulation at ambient temperature range 13.4 to 24.2˚C was associated with reduction of lactate disposal.
Shearing resulted in an increase in blood values of red blood cells, hemoglobin and hematocrit as well as a decrease in plasma volume in all ewes. Nucleated red blood cells (NRBCs) count and mean corpuscular hemoglobin concentration (MCHC) declined significantly in LHct ewes only. Low hematocrit ewes had higher percent of hematocrit (P > 0.05) and lactate (P > 0.05) increase in response to shearing, compared to HHct ewes. All blood parameters returned to normal values at 3 h after shearing.There was a significant correlation between the rates of NRBC and plasma volume decline (r = -0.66779) in response to shearing. Blood lactate levels increased in HHct and MHct ewes at 48 h after shearing compared to the respective levels at 3 h after shearing.
The data reported herein suggests that LHct ewes, unlike HHct ewes have higher capacity to cope with acute stress-induced increase in oxygen and energy demand. Also, adaptation to a lack of skin insulation at ambient temperature range 13.4 to 24.2˚C was associated with reduction of lactate disposal.
Keywords: hematocrit; lactate; nucleated red blood cells; red blood cells, mean corpuscular hemoglobin concentration; sheep; stress
Date published: 2021-08-27
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