HEMATOCRIT AS A POTENTIAL MARKER OF ACCLIMATIZATION CAPACITY AND STRESS SENSITIVITY IN SHEEP EXPOSED TO TRANSPORT AND HIGH ALTITUDE

D. Gudev, I. Yanchev, M. Dyavolova, P. Moneva

Abstract: The present study was conducted to examine the association between hematocrit, erythropoiesis and cortisol dynamics in the process of acclimatization to high altitude and during transport from high to low altitude. One hundred one Ile de France ewes were allocated into two groups following hematocrit measurement in all ewes. Group I comprised ewes with low level of hematocrit and group II comprised ewes with high level of hematocrit. Sheep were raised at low altitude (500 m above sea level). The ewes were shorn and immediately transported to high altitude (1440 m above sea level) where they were raised on pasture for 4 months during the grazing season. Blood samples were taken by jugular venipuncture several days before the shearing, at 14 d after exposure to high altitude, immediately after transport from high to low altitude and 7 days later. The following parameters were measured: hematocrit values, erythrocyte count, reticulocyte count and concentration of plasma cortisol. Hematocrit values remained unchanged in the ewes of group I through the analysis of all measurements whereas in the ewes of group II it tended to decline and reached level of significance at 7 d after transport to low altitude. Cortisol levels before shearing and by 14 d following exposure to high altitude were significantly higher in the ewes of group II as compared to the ewes of group I. Exposure to transport caused significant increase of plasma cortisol in the ewes of group I relative to baseline level whereas the increase of plasma cortisol in the ewes of group II was insignificant. Reticulocyte count at 14 d following exposure to high altitude was significantly higher in the ewes of group II as compared to the ewes of group I. The results are interpreted to suggest that hematocrit is associated with the type of hemoglobin and predominant metabolic pathway for energy supply which ultimately predetermines the pattern of hematological changes during exposure to high altitude as well as sensitivity to transport stress.

Keywords: cortisol; high altitude; reticulocytes; shearing; sheep; stress; transport

Date published: 2017-08-31