Atlas BarnFIG. 12Applied11 min

Heat stress

Heat load is temperature plus humidity, not the office thermostat. Penn State: mild heat stress starts near THI 68 — shade, air, then water.

Numbers

Measure	Value	Spread · alarm	Why it matters
Mild heat-stress THIPenn State Extension	68	Alarm: High producers already changing breath and intake	Penn State heat-abatement bulletin — start of mild heat stress for high-producing Holsteins. Humidity matters as much as the thermostat.

Field notes on this focus

Note 01THI and air speed stage the coolingBarn THI alone can miss the cow's microclimate — pair temperature-humidity with cow-level air speed so fans, misters, and soakers stage against what she actually feels.3 min · 2026-09-09

Quick check

Q 01 / 01

Penn State treats mild heat stress in high-producing Holsteins as starting near which THI?

Sources

Heat Stress Abatement Techniques for Dairy Cattle — Penn State Extension
Cooling Dry Cows to Improve Health and Production — Penn State Extension

Plate credit

System figures are educational plates drawn from public-domain veterinary teaching anatomy (udder, claw, uterus, and housing relationships). They are not scanned specimens. Educational only.

Not a veterinary diagnosis, prescription, or ration formula.