The research is being carried out in two Work Packages (WP). In WPa stress susceptibility will be tested using (1) ACTH and (2) glucose tolerance tests. In collected blood samples levels of glucose, cortisol, insulin, free fatty acids, T₃ and T₄ will be measured. Response curves of dairy calves are tested for ACTH challenge and glucose tolerance. Attempts are made to establish estimations on the relationship of growth in the rearing period and that of until first parity, and dairy performance in the first lactation. In WPb cortisol, insulin and T4/T3 response after ACTH, glucose and TRH administration is tested in mature high yielding Holstein-Friesian dairy cows post partum. The aim is to estimate (1) the extent of cortisone response to ACTH, (2) that of insulin to glucose, and (3) increase of T4/T3 level to TRH administration in relationship to (a) each other, (b) the age of animal and (c) actual milk yield in the dairy cow in the very first period of first ovulation i. e. in the physiological state as the dominant follicle develops or is atretised during the first cycle. Further aim of the study is to investigate whether response curves are altered in first ovulated cows, in hyperketonemic individuals or in animals with acute putrid endometritis.

Based on the findings of the experiments the methods of ACTH stimulation and glucose tolerance tests can be compared. A procedure will be developed to detect the connection between production ability, stress susceptibility and/or adaptation ability, representing the response to environmental load at young of age. In case of positive results, basic figures can be established for applied research for technological development and elaboration of selection methods to be applied as early as possible. Preliminary results were published to the 53^rd Annual Meeting of European Association of Animal Production (1-4 September 2002, Cairo, Egypt).

In addition, attempts are made to find out the extent of cortisol response to ACTH administration that of insulin to GTT as well as the reaction of T4/T3 to TRH load at a very early phase of first ovulation post partum between 12-15 days after delivery, when the dominant follicle develops during the first ovulation cycle or is atretised. Based on responses of animals, stimulation methods can be compared and treatment x age, treatment x milk yield interactions can be detected. Alterations of response curves in first ovulated cows, hyperketonemic animals and in cows with acute putrid endometritis can be also established.