Is Your Head Abatement System Ready for Summer?
Adapted by J.P. Martins, UCCE Dairy Advisor, Tulare & Kings Counties
With summer approaching, it’s a good time to determine if your heat abatement system is ready to keep cows cool and comfortable to avoid problems with heat stress. High-producing lactating dairy cows generate a lot of heat, and are sensitive to high ambient temperatures. Dairy cows are considered comfortable in temperatures between 40 and 70oF. As temperature rises above 70oF, cows are not able to lose heat to the environment, increasing core body temperature. To decrease body temperature, cows undergo some physiological and behavioral changes, which negatively affect productivity, health, and cow-comfort, resulting in economic losses.
During heat stress, cows significantly decrease feed intake, which causes a substantial drop in milk production. Heat stress also negatively affects reproductive performance. One way to evaluate your heat abatement strategies is to compare milk production and reproductive performance (21-day pregnancy rate, heat detection rate and conception rate) of your herd during the cold season to last year’s hot season. If there is a significant decrease in milk production and reproductive performance, you may be able to make some modifications to your heat abatement strategies and reduce the impacts of heat stress.
In a normal day, lactating dairy cows spend about 12-14 hours lying down, 5 hours feeding, and 2.5 to 3.5 hours milking. Cooling cows during these three main activities should be the focus of your heat abatement strategy. Cooling considerations for the housing area, holding pen, and water troughs are presented.
It is important to have shaded resting areas and feed lines in open lots. Since cows are lying down most of the day, and cows accumulate heat when they lay down, heat stressed cows will reduce resting time. The open lot resting area should have 38 to 48 square feet of shade area per mature dairy cow. Use fans to keep fast moving air (6 mph or greater) in this area. Portable wind meters are affordable and can be used to measure air speed. In free stall barns, measurements should be taken in several stalls at the cows’ head level when they are lying down. Air speed varies depending on several factors such as fan type, size, and potency. Space between fans should be determined by air speed. If fans are too far apart, some areas or stalls might not be getting the appropriate air velocity. Dirty fans and improper belt tension and alignment can also reduce the efficiency of fans. Fan blades should spin freely by hand. Fans also need to be angled towards the stalls (30o angle) and not parallel to the celling. The current recommendation is to set fans to turn on (and keep running) when temperatures reach 68 oF.
Evaporating water from the cows’ body surfaces is the most efficient way to remove heat from cows; fans over the feedlines and holding pen will maximize cooling after soaking the cows. Soakers should be activated every 15 minutes at 68oF, every 10 minutes at 75oF, and every 5 minutes at 85oF or above. Soaker run time will vary depending on the type, size of nozzle, and water pressure. Note the time that is necessary for your nozzle to soak the cows’ backs, and set your nozzle run time based on your notes. If nozzles are running for too long, water will drip from cows’ backs (wasted water). It takes
approximately 0.2 gallons of water per cow to soak the back of the cow. The distance between nozzles should be close to the diameter of the water spray produced by the nozzle (normally 6 to 8 feet). The objective is to reach all cows in the feed line. Make sure soakers are working properly and clean nozzles with vinegar (or other solutions) to remove particles and calcium build up before summer heat begins.
Holding Pen
Although cows spend only a few hours of the day at the holding pen, this area is critical because cows are crowded, and there is no air exchange. This is the area that cows experience the most heat stress, and one of the most important strategies is to reduce time spent at the holding pen. Fans should start running at temperatures of 65 oF and above. It is also important to measure air velocity in different areas of the holding pen. Air speed in the holding pen is recommended to be around 6 mph when cows are present. As in the resting area, number of fans and distance between fans should be based on air speed and depends on the type of fan used, holding pen area and maximum number of cows. Soakers should be on every 10 min at 68oF and every 5 minutes at 75oF or above, with run time depending on the nozzle specifications (as in the housing area).
Drinking Water
Ensure adequate amounts of clean drinking water are available to maintain hydration and avoid milk production losses during Summer. Almost 87% of milk is composed of water, making it a vital dietary requirement. Water consumption increases about 1.5 pounds for each 1oF increase in temperature. Water availability should meet the daily needs of lactating dairy cows and peak demand. Hence, it is important to ensure adequate linear water space per cow. A great strategy is to add extra waterers on the return lane from the parlor since cows drink most water right after milking. Use the following formula to calculate the required tank perimeter: group size x .15 x 2 = tank perimeter in feet.
Take-home message:
If you haven’t done so already, now is the time to start thinking about your heat abatement strategies, and make modifications to your system. It’s also a great time to check existing fans, nozzles, water lines, etc., and make any necessary repairs before consistent high temperatures are upon us. Studies have shown that heat stress during the dry period reduces milk production in the subsequent lactation, so cooling dry cows should also be a priority this summer.
Link to PDF Version: Is Your Heat Abatement System Ready for Summer