ANIMAL-RELATED AND SOME ENVIRONMENTAL EFFECTS ON DAILY MILK PRODUCTION > OF DAIRY COWS UNDER THE HEAT STRESS CONDITIONS

The study aimed to determine the effect of different fixed factors (breed, region, calving year, calving season, parity and lactation stage) on daily milk production (yield and content) of four dairy cattle breeds under the heat stress conditions (THI≥72). The research was conducted on a set of test-day records of four dairy cattle breeds (Simmental, Holstein-Friesian, Red Holstein and Brown Swiss) reared in the Republic of Serbia (Region of Mačva, Podunavlje and Šumadija). The statistical analysis included test-day records collected in the period from the beginning of the year 2012 to the end of the year 2019. Based on the performed analysis, it could be demonstrated that all the effects included in the statistical model (breed, region, calving year, calving season, parity and lactation stage) statistically highly significant (p