Building a Heat Abatement Plan for a 200-Cow Freestall Barn

A heat abatement plan is easier to build before July than during it. This article walks through a plan for a hypothetical 200-cow freestall herd, using published extension figures. The numbers for fan sizes, spacing and water are starting points. Barn layout, climate and equipment vary, so have a dealer or engineer size the final design. For background on why heat matters, see our guide to heat stress in dairy cows.

Step 1: Set the triggers

Cooling should turn on automatically at set temperatures, not when someone thinks of it. Ohio State's Buckeye Dairy News gives temperature triggers: holding-pen fans and soakers switch on at about 72 F, and freestall soaking is timed in steps, every 15 minutes at 70 to 80 F, every 10 minutes at 81 to 90 F, and every 5 minutes above 90 F. University of Missouri Extension suggests cooling begin at about 65 F, notes that intake falls above roughly 80 F, and says production can drop sharply at 90 F and above. Sources differ a little, so choose a conservative trigger, put it on a thermostat or controller, and log it. Read both sources: Ohio State and Missouri.

Step 2: Plan the holding pen first

Cows spend time packed together waiting to be milked, so the holding area is the first priority in a plan. Ohio State's figures are one 36-inch fan per 150 square feet or one 48-inch fan per 300 square feet, with fan rows every 20 to 24 feet for 36-inch fans or every 30 to 36 feet for 48-inch fans. The first row sits just outside the holding area, and fans are mounted as low as possible without interfering with equipment. Soakers in the holding area use about 1 gallon per 150 square feet, cycling 1 minute on and 5 minutes off.

Take an illustrative holding area of 3,000 square feet. That works out to 20 of the 36-inch fans or 10 of the 48-inch fans, and about 20 gallons per soaking cycle. Your holding area will differ, so measure it.

Step 3: Cool the freestalls and feed lane

Ohio State says freestall barns use the same fan spacing as the holding area, and that nozzles use about one-third of a gallon per cow per wetting cycle, with cycles typically running 1 to 2 minutes depending on nozzle size and spacing. For a pen of 200 cows, that is about 66 gallons per cycle if every cow were under nozzles at once. At the 5-minute interval above 90 F, that is 12 cycles an hour, or roughly 790 gallons an hour. Compare that figure with your well and pump capacity. Many herds discover that water supply, not fans, is the limit.

Two cautions from Missouri's guide: shorten sprinkler run times if water is dripping from udders, because wet udders raise mastitis risk, and keep the spray off the feed, because wet feed molds faster in heat. Sprinklers should wet the cow's back and shoulders, while fans evaporate the water and carry heat away.

Step 4: Size the water supply line

Ohio State's guide gives example pipe sizing based on a maximum water velocity of 5 feet per second, with nozzles 8 feet apart. A 1.5-inch pipe can serve 60 nozzles at 0.5 gallon per minute (up to 480 feet) or 30 nozzles at 1 gallon per minute (up to 240 feet), while a 2-inch pipe can serve 50 nozzles (up to 400 feet). Use these as a sanity check, then have your installer confirm the design for your pump, zones and pressure.

Step 5: Add shade, ventilation and drinking water

Missouri's guide recommends shade over feeding areas, which also increases intake, along with opened or netted sidewalls and roof venting to improve airflow. For drinking, it states a baseline of one waterer per 20 head and notes newer guidance of about 4 inches of water space per cow, which for 200 cows means 800 linear inches. Cooler water increases intake, but the value of the extra milk has to justify the cooling cost.

Step 6: Include the dry cows and fresh cows

Close-up and fresh cows are most sensitive to heat, and their pens are often the last to get fans. Include them in the plan from the start. Our article on the transition pen that works covers design details for that pen, including soaker lines at lock-ups.

Step 7: Talk to the nutritionist

Missouri's guide notes that when intake drops, nutrients must be more concentrated to hold requirements steady. It gives an example of a 20 percent intake drop that calls for higher protein and energy density, and says feeding 60 to 70 percent of the ration between 8 p.m. and 8 a.m. has increased milk production in hot weather. Those are matters for your nutritionist to adapt to your herd. See our guide to TMR and ration basics.

Step 8: Write the seasonal checklist

When	Task
Early spring	Service fans and motors, clean blades, replace worn bearings, check wiring
Spring	Flush lines, replace clogged nozzles, test controllers and sensors
Before first hot spell	Run the whole system, check water pressure, confirm triggers
Summer, weekly	Walk the barn and holding pen, check trough flow, look for dripping udders
After summer	Review conception, SCC and lameness trends against the weather

Step 9: Decide what you'd do first with a limited budget

1. Cool the holding pen with fans and soakers.
2. Put fans over the stalls and feed lane.
3. Add soaking at the feed line with a controller.
4. Fix water supply and trough space.
5. Extend to close-up and fresh pens.

The order depends on where your cows suffer most and where you have the pipe and power. For more resources, see agriculture.directory and this farm.fm story about bulk tank alarms. This site is independent and not affiliated with any breed association.