Are you ready for hot weather?
Published in Dairy Star June 13, 2009
Dairy cows are most productive at temperatures between 41 and 77° F. At temperatures above 77° F, cows begin to use energy to rid themselves of heat generated by digestion and metabolism — energy that could be used to produce milk or grow a calf if pregnant. As relative humidity increases at temperatures above 77° F, the combined heat and humidity increases the heat stress that cows experience.
Minnesota has already experienced temperatures in the 90’s. It is highly likely that your cows are going to experience hot weather this summer. Are you ready for it? What are you planning to do when the heat and humidity create heat stress? Preparing for hot weather now will help you provide exceptional cow comfort later. You can get a job done quicker and better if you have the right tools in working condition and you know how to use them. So what cow cooling tools do you have in your management toolkit? Are they in working condition? Does everyone who works with the cows know when and how to use your cow cooling tools?
Naturally ventilated barn with mixing fans pointed downward towards the cows at the feed bunk for cooling.
There are several effective cow cooling practices that you can use to help your cows get through a period of hot and humid weather.
- Shade cuts solar heat gain for cows on pasture. Cows in barns have shade. Roof overhangs provide more shade near the barn sidewalls.
- Barn ventilation cools cows by providing air exchange between inside and outside. Ventilation can be by either natural or mechanical means. In hot weather, provide as much ventilation as you can.
- Tunnel ventilation brings air in at one end or side of a barn and exhausts it out the other. Size fans and inlets correctly and make sure the fans are well maintained and inlets are open.
- Mixing fans hung from rafters or trusses create air movement during hot weather to help cool cows by blowing air past the cows. Mixing fans do not provide air exchange between inside and outside but they supplement the cooling effect of ventilation.
- Low pressure sprinklers along feed bunks or in holding areas wet the cows’ backs to provide cooling. Wet the cows’ backs to the skin. Low pressure sprinkler systems must turn on and off. Cow heat evaporates the water and cools the cows when the sprinklers are off. Mixing fans enhance the effect.
- High pressure misters cool the air by creating a fine mist or small droplets. The droplets need to evaporate before they hit the stalls or bedding. Place misters near inlets. Misters are not as effective when ventilation blows the mist out of the barn before the air cools.
- Evaporative pads cool and humidify the inlet air in low-profile cross-ventilated barns. The pads need to be uniformly moist for best effect. Fresh water needs to be added, and check for mineral accumulation and algae growth.
More information about these cooling methods is available in our facilities section.
There are several common cooling system problems to be on the lookout for as you prepare for hot weather.
- Poorly maintained fans. Numerous research studies have found that poorly maintained fans move 40 to 60% of the fans capacity. Check for slipping belts, and corroded and dirty louvers.
- Mixing fans improperly mounted may not point downward towards the cows. Several years ago, a dairy had cows die during a heat spell in a barn with mixing fans. After the loss, it was discovered that the fans weren’t pointed downward towards the cows, the air was being blown around above the cows and not providing cooling at cow level. Make sure you can feel the airflow at cow level.
- Low pressure sprinkler systems must cycle the sprinklers on and off. Sprinkling all the time wastes water, adds water to the manure system and does not help cool the cows. Cows are cooled when the sprinklers are off and the water evaporates.
- Piping for low pressure sprinkler systems have to be sized large enough to provide water to the sprinkler the farthest away from the water supply.
- High pressure misters can easily become plugged with dirt or accumulated minerals. Most systems have a filter; check the filter.
- Check the high pressure pump. Insufficient pressure leads to large droplets that do not evaporate and may wet bedding or feed.
- Evaporative cooling pads can plug with dirt, debris and algae. Check for holes in the pads that short-circuit the cooling system.
Be ready for hot weather and be cool.