What is the THI value?

The Temperature-Humidity Index (THI) measures heat stress in dairy cows. It combines temperature and relative humidity. Heat stress begins at THI 68 (mild), becomes moderate at THI 72, and critical at THI 90.

When do cows suffer from heat stress?

Dairy cows show first signs of stress at a THI of 68: increased respiration rate, reduced feed intake, and declining milk production. Stress is severe above THI 79 and critical above THI 90.

How much milk is lost during heat stress?

At mild stress (THI 68–72): 0.5–1 kg/day; moderate stress (THI 72–79): 1–3 kg/day; severe stress (THI 79–89): up to 6 kg/day per cow.

How is THI calculated?

THI = (1.8 × Temperature°C + 32) − (0.55 − 0.0055 × Relative Humidity%) × (1.8 × Temperature°C − 26). Our free calculator determines THI automatically using real-time GPS weather data.

How can heat stress in cows be reduced?

Key measures: shift feeding to cooler hours, ensure water supply (up to 160 L/cow/day), add buffer substances to the ration, install fans and sprinklers in the barn.

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