Dynamics of leukocytes and cytokines after shearing in pregnant ewes with low and high hematocrit levels

Penka Moneva, Marina Tsaneva, Ivan Yanchev, Nikola Metodiev and Dimitar Gudev

Abstract: The object of the present study was to investigate leukocyte subsets distribution and the dynamics of some pro-inflammatory and anti-inflammatory cytokines in response to shearing in sheep having different hematocrit values. Thirty Ile De France ewes were selected from an experimental herd according to their hematocrit levels 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 leukocyte subsets (basophils, eosinophils, neutrophils, lymphocytes, monocytes, large immature cells,) and cytokines (IL-2, Il-4, IL-6, IL-10, IL-17A, IFN-γ, TNF-α). 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 3 h and 48 h after shearing. Shearing elicited significant increase in neutrophil numbers in all the 3 groups at 3h after shearing followed by a return to normal levels at 48 h after shearing. Lymphocyte numbers were not influenced by shearing. There were hematocrit associated changes in basophil, eosinophil and monocyte numbers suggesting different trafficking patterns of these leukocyte subsets. Large immature cells increased significantly in all experimental animals at 3 h after shearing. Three ewes in LHct group had 3-8 fold higher levels of IFN-γ, IL-4 and IL-10 compared to the other animals in the same group suggesting pregnancy associated transition towards Th2-type cytokines. Investigated pro-inflammatory Th17 (IL-17A) and Th1 cytokines (IL-2, IL-6, IFN-γ, TNF-α) as well as anti- inflammatory Th2 cytokines (IL-4 and IL-10) were not influenced by shearing. The results are interpreted to suggest that shearing of pregnant ewes at ambient temperature below the lower critical temperature prevents cytokines increase.

Keywords: cytokines; hematocrit; interferon; leukocytes; sheep; stress

Date published: 2021-12-18