What did August’s heat cost your herd?

Denis Langlois
Sep 9
2 min read

Open your Horizon “Group Daily Heat Stress” graph and find out.

Why this matters (local data)

In a Fraser Valley multi-farm project, herds spent over half of the May–Sept period in some level of heat stress; more than one‑third was moderate to severe. Heat stress in dairy cattle starts around THI 68—well below “heat‑wave” temps.
The biggest lever wasn’t luck—it was airspeed over the stalls. Farms with >50% of stalls at ≥2 m/s saw only ~‑1.7% drop in fat‑corrected milk during the major heat event, while farms with poor airflow (<20% of stalls ≥2 m/s) lost ~‑7.5%—about $2.78 per cow per day at the prices used in the study.
UW–Madison’s Dairyland Initiative recommends 1–2 m/s over all resting areas; in local barns, re‑aiming or adding fans around obstructions (robot rooms, high rafters, sort pens) moved the needle.

Do this today (it takes 10 minutes)

Open Horizon → Group Daily Heat Stress. Scan the last month. Do you see blue heavy‑breathing spikes with a dip in rumination/eating and a sag in Day Production right after? Screenshot it for your notes.
Circle the dates where the lines diverge the most. That’s your on‑farm evidence to act.

Your winter ventilation game‑plan

Measure, don’t guess. Buy a $50 handheld anemometer and map airspeed 24" above the stall surface at max ventilation (every ~5 stalls). Mark low‑speed zones (<2 m/s).
Fix the shadows. Re‑aim fan angles, add re‑directional fans near robot rooms/sort areas, and remove airflow obstructions. Target ≥2 m/s across as many stalls as possible.
Plan water + wind. If you use misters/soakers, pair them with strong airspeed so water evaporates off the cow—otherwise you just add humidity.
Order in winter. Fan supply tightens every spring; winter is the smart time to spec, order, and install so you’re ready for next summer.

How we can help?

West Coast Robotics can help you read your Horizon heat‑stress trends, map barn airspeeds, and design a ventilation upgrade that hits the ≥2 m/s target where cows lie down.

Want a quick read? Email us your Heat Stress screenshot and we’ll recommend a winter fan plan for your barn layout.

References

1. Managing Extreme Heat on Fraser Valley Dairy Farms. West Coast Robotics for BC Dairy Association, March 2023.