Eight Clun Forest wethers were used to study the effects of feed and/or water deprivation at different ambient temperatures (7 or 35 degrees C) on stress hormone release. Blood samples were taken from catheterized animals at the start and at 6 h intervals during 48 h tests in an environmental chamber. Cortisol release was unaffected by temperature or deprivation state but was stimulated by introduction to the chamber. Prolactin secretion showed a similar tendency and levels of this hormone were generally higher in the first test, whichever chamber was used. Heat exposure also had a prolonged stimulatory effect on prolactin release, especially in the first test. Somatotropin concentrations were variable but tended to be greatest when the animals were deprived of food. Measurements of plasma osmolality indicated that sheep remained in water balance, even when water was withheld for 48 h, unless they had access to food. It is suggested that under laboratory conditions, and over a wide thermal range, withholding feed and water for 48 h does not induce cortisol or prolactin release in sheep. However, exposure to novel situations seems to have a stimulatory effect.
|Publication Title||Animal Welfare|
|Author Address||MAFF Welfare and Behaviour Laboratory, Babraham Institute, Cambridge CB2 4AT, UK.|
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