BY JOHN E. HALL Extension Agent, Ag Science Several methods are used on today’s farms to reduce heat stress on dairy cows. These methods in clude providing, 1) clean water readily available, 2) shade, 3) ade quate natural or forced ventilation, 4) altered feeding strategies, and 5) sprinkler and fan evaporation cooling. Most dairymen have incorpor ated many of their procedures into their summer practices. Many dairymen have tried to provide sufficient shade, many have built roofs or shade over their feed bunks and several have increased the feeding frequency during the summer. Many have also tried to incorporate some type of sprinkler system into their heat stress man agement. Two areas for using the sprinkler system are in the holding area and over the cows when they are at the feed bunk. 1 would like to focus on the sprinkler system at this time be cause I believe most producers are still doing it wrong. Sprinkling is more effective when combined with air movement This allows the haircoat to function most effi ciently as an evaporative cooling pad. If a light mist or fog is ap plied continually on the cows, the water foims an insulating blanket that raises, rather than lowers, body temperature. The sprinkler system - DO NOT Mist or Fog: The object here is to get enough moisture on the cow to penetrate the hair coat and reach the skin. Again, if the moisture does not penetrate the haircoat, water forms an insulating moisture blanket that raises, rather than lowers, body temperature. Water pressure and nozzle selection are keys to applying water. Spray Nozzles: Two types have been used in current research . .. A) Solid-cone, low pressure Keep Your Cows Cool Not Cooked agricultural spray nozzles (0.062 S in. orifice diameter) rated at 0.6 gal/min at 10 psi mounted 4-5 ft. above the cows approximately S.6’ apart (avoid spraying on feed in bunk) have been used effective ly. B) Low pressure, 180 deg. plas tic spray nozzle with 0.22” dia meter orifice can also be used. At 10 psi pressure the nozzles have an 8’ spray radius. Thus, nozzles should be placed approximately 8’ apart. With each nozzle, it appears from the literature that a low pres sure system with a larger nozzle is preferred. This means incorporat ing a pressure reducing valve into the system. I would also sug gest some type of filter system to avoid clogging the nozzles. Air Movement Sprinkling is more effective when combined with air move ment. This allows the haircoat to function most efficiently as a eva porative cooling pad. An air velocity of about 400 to 600 feet per minute over the cows is recommended from Florida stu dies. At least one 36-inch fan for each 40 cows is needed to provide this velocity. More fans may be required in areas where cows are grouped closely, such as holding area. Each fan should provide 11,000 cubic feet per minute of air flow when it is operating in free air. A fan of this type will move air ef fectively for a distance of about 10 fan diameters or 30 feet. This ar rangement suggests this type of fan be hung every 16’ when used near the feed bunk and tilted slightly downward to direct the air onto the cows. This no doubt seems excessive; however, we must remember that the humidity on the Delmarva Peninsula reaches near saturation many days. Thus, we must in crease the volume of air over the cows to effectively evaporate the moisture. Other studies have been com- pleted in Kentucky using smaller 18 in. diameter fans connected to a polyethylene tube 18’ long. Holes were cut in the tubes to force air directly onto .the cows. This sys tem provided air flow to reach ve locities of 208 ft./minute over the cows. As you read other articles about this subject, you will see that the air velocity recommended will range from 200 to 600 ft. minute. Be sure to read where the research was completed and what the aver age relative humidity during the test was. Again, I repeat, as humidity increases, velocity must increase accordingly to effectively evaporate this moisture. The Key - Alternative The key to this type of system is altering water with air. Get them wet then blow them dry. This is the key point that we have over looked here on Delmarva. It ap pears a cycle of about 1 part water to 5 parts air is most widely used. In the studies that I reviewed, it appears that the water to air cycle can range from 1 min. water to 5 min. air up to VA min. water to 13.5 min. air. Two key points when setting your cycle are: 1) How much time does it take the cows to get wet to the skin?; 2)How much time does it take the fans to blow them dry? The Controller: To effectively operate this sys tem of water/air in this intermit tent fashion, you need to incorpor ate 1) solenoid valve, 2) thermostat, and, 3) a timer. Control boards are currently be ing used to cool hog and poultry bams. Some units come complete ($375.00) and others can be pre pared by attaching the individual components on a board ($125.00). The Sollenberger UPRIGHT BUNKER SILO It appears that these units should be set to operate when the temperature reaches 78-80 deg. F. Timing the water flow in this fash ion also has the added advantage of reducing the amount of water that flows into the manure system during use. In conclusion, producers must decide if they are going to use wa ter cooling or evaporative cooling. Evaporative cooling is the only method shown to be effective. However, evaporative cooling means applying water and air in an Office Number - 717-264-9588 For Upright Silos C«II For Bunker Silos & Manure Systems Bob Francis Call Tabb Justua orMtkeHalr 717-532-6848' 717-762-8663 717-263-0792 Clinton Co. DHIA March, 1990 Rolling Hard Averaga No. % Days Milk Fat Name Brd. Cows In Milk Lbs. Lbs. Ronald H Meyer B 3 111.8 88.9 19,916 751 Paul L Courier 3 71.1 87.2 19.886 731 Blair&Elaine Courier 3 71.2 88.0 19,367 698 Richard L Schenck 3 123.9 86.0 18,468 690 Robert Billman B 3 32.4 86.9 17,796 677 Jacqueline Seyler B 3 44.2 89.2 17,784 652 Lactation Report Ronald H Meyer #lOB • Fast installation • Low Cost • Durable • Moveable • Attractive • Quality Storage lor corn silage, haylage and high moistura ground ear corn • Other usea Storage for bulk materials, retaining walls and manure pits Evenings intermittent fashion. Get them wet to the skin, then dry them off. Thus, to properly set this system up, select the proper nozzle, place them to reach all animals, incor porate the correct pressure and use a filter system. Fans then need to be placed to blow air at 200 to 600 ft./minute over the cows. The key to the system is a controller that includes a solenoid valve, thermo stat and timer. For more informa tion, call the Extension Office at 778-1661 or 758-1107. Monthly Report 305 20,233 857 Tonguo A Groovo Joint Soctlono Bolt Togothor Approximate Wol(M> S7SO I bo.
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