The effect of 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, season, parity and lactation stage) on daily milk production (yield content) four dairy cattle breeds under heat stress conditions (THI?72). research was conducted a set test-day records (Simmental, Holstein-Friesian, Red Holstein Brown Swiss) reared in Republic Serbia (Region Ma?va, Podunavlje Šumadija). statistical analysis included collected period from beginning year 2012 end 2019. Based performed analysis, it could be demonstrated that all effects model statistically highly significant (p<0.001) affected cows terms conditions. highest determined region Podunavlje, by Holstein-Friesian breed. Furthermore, calved during spring third 61st 120th day lactation, had summer an environment characterised stress. Also, yield decreased June September. results obtained indicate animals' responses concerning animal's breed, rearing stage.