Acclimatization to moderate altitude in ewes having low or high hematocrit levels
Penka Moneva, Ivan Yanchev, Nikola Metodiev, Marina Tsaneva, Dimitar Gudev
Abstract: The object of the present study was to investigate the acclimatization strategy to mild hypoxia in
ewes having low or high hematocrit levels. Ile De France ewes were selected according to their levels
of hematocrit and then were allocated into two groups. Group I comprised ewes with low hematocrit
level (n-10) and group II comprised ewes with high level of hematocrit (n-10). Immediately after
the shearing, performed at the experimental unit of the Institute of Animal Science, Kostinbrod,
(altitude of 500 meters) the ewes were transported to a mountain pasture at altitude of 1440 m where
they were raised for 4 months (June–September). Blood samples were collected via venipuncture at
the following time points: before shearing, immediately after the transport, on day 5, 10, 30 and 60
after the transport. The following indices were measured: plasma cortisol, hematocrit, total leukocyte
count, erythrocyte count and reticulocyte count. Adrenal response to transport and exposure to
altitude was significantly higher in high-hematocrit ewes relative to low-hematocrit ewes. The higher
hematocrit level in the ewes of group II persisted throughout the experiment. The ewes having high
hematocrit level had higher cortisol concentration immediately after transport and during the rest of
the experimental period as compared to low-hematocrit ewes. Erythrocyte count tended to be higher in
high-hematocrit ewes throughout the experimental period. Reticulocyte count increased significantly
as compared to basal count and remained elevated in both groups at the mountain pasture. There was
distinct difference in the reticulocyte number dynamics among the groups. Leukocyte count tended
to be higher in the high-hematocrit ewes immediately after transport and on day 5 and 10 following
exposure to altitude. The observed trend reached significance on day 30 and 60. It was concluded that
basal hematocrit level is related with the pattern of adrenal and hematological adjustments of newly
shorn ewes to moderate altitude.
ewes having low or high hematocrit levels. Ile De France ewes were selected according to their levels
of hematocrit and then were allocated into two groups. Group I comprised ewes with low hematocrit
level (n-10) and group II comprised ewes with high level of hematocrit (n-10). Immediately after
the shearing, performed at the experimental unit of the Institute of Animal Science, Kostinbrod,
(altitude of 500 meters) the ewes were transported to a mountain pasture at altitude of 1440 m where
they were raised for 4 months (June–September). Blood samples were collected via venipuncture at
the following time points: before shearing, immediately after the transport, on day 5, 10, 30 and 60
after the transport. The following indices were measured: plasma cortisol, hematocrit, total leukocyte
count, erythrocyte count and reticulocyte count. Adrenal response to transport and exposure to
altitude was significantly higher in high-hematocrit ewes relative to low-hematocrit ewes. The higher
hematocrit level in the ewes of group II persisted throughout the experiment. The ewes having high
hematocrit level had higher cortisol concentration immediately after transport and during the rest of
the experimental period as compared to low-hematocrit ewes. Erythrocyte count tended to be higher in
high-hematocrit ewes throughout the experimental period. Reticulocyte count increased significantly
as compared to basal count and remained elevated in both groups at the mountain pasture. There was
distinct difference in the reticulocyte number dynamics among the groups. Leukocyte count tended
to be higher in the high-hematocrit ewes immediately after transport and on day 5 and 10 following
exposure to altitude. The observed trend reached significance on day 30 and 60. It was concluded that
basal hematocrit level is related with the pattern of adrenal and hematological adjustments of newly
shorn ewes to moderate altitude.
Keywords: acclimatization; cortisol; hematocrit; leucocytes; reticulocytes; sheep
Date published: 2022-11-02
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