Bulgarian Journal of Agricultural Science
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Endocrine responses to moderate altitude hypoxia in pregnant Ile de France sheep with low or high basal hematocrit levels
Penka Moneva, Ivan Yanchev, Nikola Metodiev
Abstract: The object of the present study was to investigate some hormonal responses to mild hypoxia. Thirty Ile De France ewes were selected according to their hematocrit level and were allocated into 3 groups: low hematocrit (LHct) (hematocrit range - 19.7-27.9%), high hematocrit (HHct) (hematocrit range - 32.0-36.9%) and mean hematocrit (MHct) (hematocrit range - 28.3-29.8%). Immediately after shearing, ewes were transported from the Institute farm (altitude 500 m) to a mountain pasture (altitude 1440 m). Blood samples were taken by jugular venepuncture at the following time points: before transportation (baseline level), on day 7, 20 and 42 after the transport. The traits investigated were blood cortisol, thyroid hormones (T3 and T4), growth hormone, reticulocyte count and lactate. Moderate altitude exposure resulted in significant increase on day 7 in plasma cortisol levels in LHct ewes (P<0.05). Cortisol levels increased significantly on d 20 in HHct and MHct ewes (P<0.05) compared to baseline levels. Thyroxine levels in LHct and MHct ewes were significantly higher on d 7 as compared to baseline levels (P<0.05). Triiodothyronine in LHct and HHct ewes declined significantly at 20 d compared to baseline level. (P<0.05). Growth hormone levels declined significantly in HHct ewes on d 42 as compared to baseline levels (P<0.05), while in LHct and MHct ewes remained unchanged. Corrected reticulocyte count was significantly higher in HHct ewes compared to LHct ewes at 7 d (P<0.05). There was a general trend of a slight decrease in T3 and T4 levels in all ewes at 20 d and 42 d. Blood lactate levels increased significantly in LHct (P<0.001) and HHct ewes (P<0.05) at d 7 compared to baseline levels. Lactate levels on d 20 d and d 42 in LHct ewes and HHcrt ewes declined but remained significantly higher compared to baseline leves (P<0.05). There were significant correlations on day 7 between: GH and T3 (r=0.503; P<0.05); GH and lactate (r=0,574; P<0.01); T3 and lactate (r=0.517); P<0.05). In conclusion, Adaptation of shorn pregnant ewes to moderate altitude hypoxia was associated with a slight decrease in basal metabolism accompanied by a slight increase in lactate level.
Keywords: cortisol; GH; lactate; reticulocytes; sheep; stress; T3; T4
Citation: Moneva, P., Yanchev, I. & Metodiev, N. (2023). Endocrine responses to moderate altitude hypoxia in pregnant Ile de France sheep with low or high basal hematocrit levels. Bulg. J. Agric. Sci.,29(6), 1128–1136.
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Date published: 2023-12-15
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