Summary
The objectives of this study were to determine the microclimatic conditions in stables in three
climactic regions (East, Mediterranean, and Central) of Croatia as well as to evaluate the effect of
temperature-humidity index (THI) values on the daily production of dairy cattle. With that purpose,
1675686 test-day records collected from January 2005 until April 2010 were extracted from HPA
(Croatian Agricultural Agency) database. For estimation of the effect of THI on daily production
of dairy cows fixed-effect model that took into account the effects of lactation stage, breed, calving
season, measuring season, and THI group (T1 - THI≤72; T2 - THI>72) was used. Model was applied
to each class of parity (P1, P2, P3, P4 and P5) and region. During the analysed period, the highest
monthly averages of ambient temperature were determined in Mediterranean region, the highest
monthly averages of relative humidity were observed in Central region, while the highest monthly
mean values of temperature-humidity index (THI) were determined in Mediterranean region. Heat
stress conditions indicated with mean daily values of THI>72 were determined during spring and
summer season in all analysed regions. Absence of heat stress conditions during autumn and winter
season also characterised all three regions. Highly significant (P