Hair Cortisol Levels to Monitor Hypothalamic-Pituitary-Adrenal Axis Activity in Healthy Dairy Cows.

The objective of this study was to evaluate hair cortisol levels in healthy Friesian dairy cows. The trial was conducted on 229 multiparous lactating Italian Friesian dairy cows from 90 to 305 days of lactation selected from a single herd. The animals were clinically healthy and had not undergone social group changes or any disease occurred within the past 3 months. Hair samples were obtained by clippers from the animal’s forehead and hair cortisol concentration was evaluated by RIA. The hair cortisol concentrations ranged from 0.8 to 20.41 pg/mg. In 50% of the animals, cortisol levels were below 3.13 pg/mg. The cows were classified into fourteen classes according to their hair cortisol levels and percentage frequencies for each class were calculated. The 33% of the animals were concentrated in the hair cortisol class 2-2.99 pg/mg. This preliminary study describe the distribution of hair cortisol levels in healthy Friesian dairy cows and suggest hair cortisol analysis as an interesting and useful tool to monitor HPA axis activity in healthy lactating dairy cows.