Radioimmunoassay technique for measuring cortisol in milk

Area of Science:

• Veterinary Medicine
• Endocrinology
• Dairy Science

Background:

• Cortisol, a key stress hormone, plays a crucial role in animal physiology and health.
• Accurate measurement of cortisol in milk can provide insights into animal welfare and stress levels in dairy herds.
• Existing methods for cortisol analysis in milk may be complex or time-consuming.

Purpose of the Study:

• To develop and validate a sensitive radioimmunoassay (RIA) for quantifying cortisol concentrations in bovine milk.
• To assess the feasibility of using skim milk for cortisol analysis, simplifying the procedure.
• To establish baseline cortisol levels in skim milk and colostrum from dairy cows.

Main Methods:

• A sensitive radioimmunoassay (RIA) procedure was optimized for the direct measurement of cortisol.
• Cortisol concentrations were compared between whole milk and skim milk samples.
• Milk samples were collected from seven cows over one week at different times (2400 h and 1200 h) to determine diurnal variations.

Main Results:

• Cortisol concentrations were found to be similar in both whole milk and skim milk, indicating minimal association with milk lipids.
• Mean cortisol concentrations in skim milk were 0.71 +/- 0.05 ng/ml at 2400 h and 0.69 +/- 0.07 ng/ml at 1200 h.
• Cortisol levels in colostrum averaged a higher concentration of 1.59 +/- 0.07 ng/ml.

Conclusions:

• The developed RIA is a sensitive and reliable method for measuring cortisol in bovine milk.
• Utilizing skim milk for cortisol analysis offers a simplified and faster approach compared to whole milk.
• This method facilitates easier monitoring of cortisol levels in dairy cows, aiding in stress assessment and herd management.