Relationships between temperature-humidity index and the cheese-making potential of dairy milk in temperate environments

In response to climate change, indoor stalling challenges, and the sensitivity of dairy cows to elevated temperatures (often initiated at THI > 68), previous research has primarily targeted the effects of elevated THI, creating a gap in knowledge regarding low THI. Yet, freezing winters still reduce milk quality and productivity of high-yielding cows. This study investigates the association between different THI classes (< 40, 40–70, and > 80) on the yield, composition, and technological properties of milk from temperate-climate dairy cattle by analyzing 867 records across two years from 338 healthy cows in three herds. THI classes were associated with milk yield and its adjusted yields ( p < 0.01, p < 0.05). Milk production was highest within THI 40–70. Fat-corrected milk (FCM) yield peaked under high thermal conditions (THI > 80, p < 0.01), whereas value-corrected milk (VCM) and laboratory curd yield significantly decreased as THI rose ( p < 0.01). THI did not affect coagulation time or visual quality scores. Somatic cell count (lnSCC) and free fatty acids remained stable across all groups. Therefore, temperate-climate breeding programs and immediate herd management strategies must mitigate these challenges. This should enhance cow resilience to THI extremes, which is crucial for high-yielding breeds like Holstein-Friesian.