Index of welfare, housing systems and hair cortisol level in dairy cows.

There is increasing interest in animal welfare topics and the question on how to measure it is still under debate. Dairy cattle are often challenged with stressful practices but housing conditions are among the most important. Determination of hypothalamus- pituitary-adrenal axis activity evaluates stress conditions in farm animals, however, blood cortisol concentrations vary due to several factors and the release of cortisol is generally irregular and difficult to interpret. The use of hair as a suitable biological matrix to assess chronic stress in animals has been recently proposed by many authors.