24 April 2023

6 minute read

By: Emily Fread

North America

It has been well established in the dairy industry that heat stress negatively affects all animals on the farm during the summer. Lactating cows experience fluctuations in fat and protein yields, as well as lowered milk production and dry matter intake. Heat stress in dry cows leads to shorter gestation lengths, challenging transition periods, and reduced production in the subsequent lactation. Heat stress in calves and heifers affects growth rates and disease. It is essential to provide heat abatement to all animals on the farm, regardless of age group or stage of lactation. Heat abatement can be supplied in three ways: shade, air, and water.

Shade

Shade can be provided on pasture with trees or a shade structure. When shade is provided on pasture, it has been shown to decrease aggressive behaviors toward other animals and increase rumination, grazing, and resting time (Kendall et al., 2006; Vizzoto et al., 2015). Shade can also increase milk production when provided for lactating animals on pasture. There are several variables to consider when building shade structures: whether they will be permanent or moveable and the cost of materials. Some producers employing rotational grazing practices may want to move their shade from pasture to pasture. Many portable shade structures are built with a steel frame and can be pulled around pastures with equipment or are collapsible for easy transport. Mobile shade structures can be constructed with corrugated steel coverings or shade cloth. 

Shade cloths must be replaced every few years due to damage; corrugated steel may have a higher initial investment, but it also has a longer life than shade cloth. When summer is over, consider what will happen to your shade structures over the winter. If your system includes a shade cloth, it can be ripped or damaged by the weight of snow, so the shade cloth should be removed, or the structure should be collapsed before winter weather. If shade structures are left on pasture over the winter, they should be inspected in the spring to assess any damage and need for replacement. Shade cloths should also be inspected at the end of the summer season to assess damage due to birds.

While shade looks straightforward in a barn, it is essential to consider where the sun shines into pens at different times of the day. Ideally, barns should be oriented east-west to prevent solar radiation from shining in (Tyson, 2017), but that is only sometimes possible due to land constraints and the direction of prevailing winds. If the sun is shining into the barn during hot summer days, adding a shade cloth to the side of the barn may be beneficial. This shade cloth could prevent cows from bunching at one end of the pen to be out of the sun's reach. When putting a shade cloth on the sidewall of a barn, ventilation must be considered. 

Since a shade cloth could block ventilation, it should be movable and taken down when the sun is not shining into the barn; it should also be removed or rolled down before winter. Another option would be putting a shade cloth on the outside of the barn parallel to the ground to move the shade line out from the barn; this option may be preferable as it would not block any air exchange. Similar to shade clothes on pasture, they should be inspected regularly for bird damage.

Ventilation

Air exchange and velocity are paramount considerations for heat abatement when animals are housed in a barn. Providing animals with air exchange adequate for normal breathing and behaviors and enough air velocity to cool them during the summer is essential. Air exchange can be accomplished during the summer using tunnel or natural ventilation; circulation fans can increase air velocity. Fans and tunnel ventilation can only cool cows if functioning correctly, meaning maintenance should be performed to ensure this; dirty fans are less efficient. Spring fan maintenance should include cleaning all fan parts: blades, air inlets, motors, etc. 

All parts, including blades, belts, and cords should be inspected and replaced if damaged. The fan's manual from the manufacturer should also be checked to ensure proper lubrication (Huyser, ISU Extension and Outreach). The angle of fans should be considered when conducting fan maintenance. Your nutritionist or local extension educator may have an anemometer capable of measuring wind speed. Wind speed should be measured at cow lying and standing heights in stalls and standing height at the feed bunk. If wind speed is not at least five mph at lying and standing heights, fans may need to be reangled to a 15 to 20-degree angle (Tyson, 2017). Similar maintenance should be performed on exhaust fans in tunnel ventilation systems.

Water

Water is arguably the most important form of heat abatement for cows during the summer. One of the best ways a cow can cool herself down is by drinking cold water. When water is hot, it does not cool cows as much or as long as when they drink cold water (Bewley et al., 2008). If possible, water tanks should be placed underneath a shade structure on pasture to keep water temperatures cool and encourage drinking behavior. Dairy cattle will drink five to six more gallons of water on a hot day (Jones et al. 1999), so enough water should be provided for all animals, meaning 2.5 to 3.5 inches of trough space per animal (Tyson, 2017). 

Water tanks should be checked on hot and cool days to see if the refill rate is high enough or if cows are waiting for a drink. Additional tanks may be considered for the summer if the tanks are not refilling fast enough. Water tanks should also be checked regularly for cleanliness, as some animals may like to stand in water to cool down during the summer. Water tanks should be cleaned regularly to prevent the spread of disease on your farm. If cows are standing in waterers regularly during the summer, a guard rail could be added around the tank similar to a feed rail.

Water can also be utilized as a form of heat abatement through sprinklers/soakers. Not only can sprinklers increase milk production in lactating cattle, but they can also increase dry matter intake in all animals on the farm during heat stress (Igono et al., 1987). When sprinklers are located at the feed bunk, dairy cattle will spend an extra hour eating daily, offsetting some of the reduced dry matter intakes that come with heat stress (Chen et al., 2013). To perform spring maintenance, sprinkler lines, and sprinkler heads should be checked for debris and cleaned to ensure that water can flow out at an appropriate pressure. Debris may be a more prevalent problem if hard water is present on your farm. Pipes should also be checked for leaks and replaced if needed to conserve water.

In conclusion, heat abatement is essential for every dairy animal, but it is only beneficial if it works properly. Spring maintenance should be performed on the three critical forms of heat abatement: shade, air, and water. When a heat abatement system works correctly, it can improve dairy welfare and animal performance.

Headline image courtesy of Cassie Yost & Emily Fread, Penn State Extension