Endocrine responses to shearing stress in pregnant Ile de France ewes with low and high basal hematocrit levels
Penka Moneva, Marina Tsaneva, Ivan Yanchev, Nikola Metodiev and Dimitar Gudev
Abstract: The object of the present study was to investigate some hormonal 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 blood cortisol, thyroid hormones (T3 and T4), growth hormone and lactate. 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 plasma cortisol in all ewes. The ewes with high baseline hematocrit level had lower percent of cortisol increase in response to shearing compared to MHct (P < 0.05) and LHct ewes (P > 0.05). Thyroxine level in LHct tended to be higher during the entire experimental period and was significantly higher compared to MHct ewes at 3 h following shearing (P < 0.05). Triiodothyronine in HHct ewes declined at 48 h after shearing (P < 0.05). There was a general trend of a slight decrease in T3 and T4 levels in all ewes at 3 h and 48 h after 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. In conclusion, Adaptation to a lack of skin insulation at ambient temperature range 13.4 to 24.2°C was associated with a slight decrease in basal metabolism accompanied by a slight increase in lactate level.
Shearing resulted in an increase in plasma cortisol in all ewes. The ewes with high baseline hematocrit level had lower percent of cortisol increase in response to shearing compared to MHct (P < 0.05) and LHct ewes (P > 0.05). Thyroxine level in LHct tended to be higher during the entire experimental period and was significantly higher compared to MHct ewes at 3 h following shearing (P < 0.05). Triiodothyronine in HHct ewes declined at 48 h after shearing (P < 0.05). There was a general trend of a slight decrease in T3 and T4 levels in all ewes at 3 h and 48 h after 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. In conclusion, Adaptation to a lack of skin insulation at ambient temperature range 13.4 to 24.2°C was associated with a slight decrease in basal metabolism accompanied by a slight increase in lactate level.
Keywords: cortisol; growth hormone; lactate; sheep; stress; thyroxine; triiodothyronine
Date published: 2021-10-19
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