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Updated: Jul 11, 2026
04:33
Primary Culture of Rat Adrenocortical Cells and Assays of Steroidogenic Functions
Published on: March 12, 2019
Rams with poor feed efficiency are highly responsive to an exogenous adrenocorticotropin hormone (ACTH) challenge
S A Knott1, L J Cummins, F R Dunshea
1Faculty of Land and Food Resources, The University of Melbourne, Parkville, Victoria 3010, Australia.
Domestic Animal Endocrinology
|September 11, 2007
Summary
Less feed-efficient sheep exhibit a heightened stress response, indicated by increased cortisol levels after adrenocorticotropin hormone administration. This suggests a link between energy utilization efficiency and physiological stress mechanisms in sheep.
Area of Science:
- Animal Physiology
- Metabolic Efficiency
- Endocrinology
Background:
- Stressors activate the hypothalamic-pituitary-adrenal axis, increasing metabolic rate and energy consumption in animals.
- Energy utilization efficiency is a critical factor in animal production and health.
- The relationship between an animal's energy efficiency and its stress response requires further investigation.
Purpose of the Study:
- To test the hypothesis that less feed-efficient sheep exhibit a greater stress response to exogenous adrenocorticotropin hormone.
- To investigate the correlation between feed efficiency metrics and adrenocorticotropin hormone-stimulated cortisol levels in sheep.
- To explore the association between an animal's stress response and its body composition.
Main Methods:
- A pilot study determined optimal adrenocorticotropin hormone dosage and cortisol response time in sheep.
- Adrenocorticotropin hormone was administered to a larger cohort of sheep (n=50) with known feed efficiency (feed conversion ratio, residual feed intake).
- Serum cortisol levels and body fat proportion were measured post-adrenocorticotropin hormone administration.
Main Results:
- Less efficient sheep (higher residual feed intake) showed a significantly greater increase in cortisol concentration compared to more efficient animals (P<0.001).
- Sheep with higher cortisol levels also exhibited a greater proportion of body fat (P<0.001).
- A significant relationship was demonstrated between residual feed intake and the animal's stress response.
Conclusions:
- Feed efficiency, measured by residual feed intake, is significantly associated with an animal's physiological stress response.
- These findings provide insights into the physiological mechanisms underlying energy utilization efficiency in sheep.
- Identifying animals with superior feed efficiency may be aided by assessing their stress response.
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