Managing in the heat

Cool season preparation

Check evaporative cooling: are you doing all you can?

Having investigated options to inrease shade, the next thing to consider is evaporative cooling. Evaporative cooling involve the use of sprinklers, fans or a combination on cows on yards or feed pads with or without a shade shelter to increase air flow and overcome the limitations of cows trying to cool themselves by evaporation (sweating).

It is important to understand the difference between the main types of evaporative cooling systems:

System	How it works	Comment
Fan and pad	Works by spraying very fine water droplets into the air, cooling the air as the droplets evaporate.	Used in many greenhouses Suitable for housed dairy systems Very efficient, but expensive
Fog	Works by spraying very fine water droplets into the air, cooling the air as the droplets evaporate.	Very efficient, but expensive. May exacerbate humidity problems.
Mist	Works like the fog system, but uses a larger droplet size that drops slowly to the floor, evaporating as it falls, rather than staying suspended in the air.	Effective, but difficult to use in windy conditions or with fans. Can cause cow health problems if used in enclosed areas.
Sprinkling	Works by wetting the cow's hair coat to the skin. The water then evaporates and cools the cow's hair and skin.	A moderate to large size water droplet is essential

Cows off-load most of their heat through evaporation from sweat and breathing. Anything you can do to assist their evaporative cooling processes is worthwhile.

To be effective, sprinklers must wet the cows' hair coats to the skin. Good air movement is also essential.

Sprinklers

Every dairy yard in Australia should be fitted with sprinklers. Many farmers find they not only improve milk production, they also make for more contented cows during milking, with better milk let down, while also reducing fly problems. This is especially true when cows are breathing at more than 60 breaths per minute or the Temperature Humidity Index (THI) is above 78. See Go on alert for more information.

Pluses		Minuses
√ √	Can be mounted in dairy yard, or a feed pad if it has a concrete floor. Relatively cheap to fit.	X	If droplet size is too small cooling will not be effective
√	With appropriate positioning, effective at cooling large numbers of cows at one time.	X	Use in high humidity conditions actually increases heat load on cows

If you have a shade shed / feed pad with a concrete floor and facilities to collect and handle run-off, sprinklers can be very effective. A roof over the area where cows are to be sprinkled is ideal, as it eliminates direct solar radiation. Be sure to provide food and water close to/in the cooling area. The cooling system can only be effective if it increases feed intake and, therefore, milk production. The sprinkler nozzles should be directional, if possible, so they can be adjusted if the direction of the prevailing wind shifts to reduce the wetting of feed.

Dairy yard cooling

Sprinkling cows

Caution: Cooling using sprinklers is not effective unless there is adequate air movement. Poor ventilation in conjunction with water cooling will only result in high humidity and may lead to herd health problems.

On hot days, sprinkle cows for 30 to 60 minutes while they are standing in the yard waiting for afternoon milking. The hotter the cows, the longer the cooling time. Sprinkling cows at the morning milking may also be beneficial if relative humidity is high and the cows’ breathing rate is more than 60 breaths per minute.

Run sprinklers ‘two minutes on and 10 minutes off’ to ensure good yard coverage, but conserve water.
Aim for a medium-to-large droplet size, rather than a fine mist. Remember, the cows’ skin needs to be wet for the sprinkling to be effective.
Sprinklers should cover the entire dairy yard, so that all cows are wet effectively.
Cows should not be packed too tightly, to ensure air movement is sufficient to allow evaporative cooling to occur.
Allow cows’ teats time to dry or dry them with a paper towel before putting cups on.
Avoid wetting cows immediately after milking to prevent teat disinfectant from being replaced with contaminated water while teat orifices are still open.

Wetting concrete

Wetting the concrete by hosing, flood washing or sprinkling for the hour prior to cows arriving at the dairy yard helps dissipate the heat stored in the mass of the concrete.

Use a 'two minutes on / five minutes off' regime to conserve water.

Remember that the longer cows stand wet in the yard before they enter the dairy to be milked, the more heat they will unload.

Providing shade

Remember that shade is always king! Even if you are using sprinklers, consider planting trees on western side of the dairy and installing a shade cloth over the yard to reduce solar radiation. The combination is especially effective if little paddock shade is available.

Fans	Water cooling will not be effective unless there is some air movement, so fans are a cheap way of providing air circulation. In shade sheds fans can be arranged in many ways, but should direct air flow with the prevailing wind. The size of fans and direction they face may depend on the spacing of the posts in the shed. Seek professional advice. Fans should be tilted about 30º from the vertical, so that they blow down to the floor directly under the next fan.
Combinations: Sprinklers & Fans	Under severe heat stress, soaking every five minutes with fan cooling will be the most effective; under periods of moderate stress, soaking every 10 minutes with fan cooling may be adequate. The combination of soaking and fan cooling is superior to either single treatment. Used alone, soaking has more impact than fan cooling.
Paddock cooling under centre pivots / water cannons	On sandy soils and on quality pasture, allow cows to move in and out of centre pivot irrigation systems. Cannon spray units also an option if water available.
Access to dams	As a last resort, in emergencies, dams are an option. Dams with water flow in and out preferable. However, this option does increases the risk of mastitis in cows aroung calving times.

See further information, for more details on sprinkler system components.