Heat stress in cattle due to elevated temperature and humidity in the summer months is documented to reduce productivity in dairy cattle. In beef production the losses of production have been slight or imperceptible to most studies. However as stewards of our animals this article will provide you with some points to consider if you would like to develop shaded areas in pens to improve comfort and promote the highest production possible in your animals.
Cattle are exposed to 3 primary heat sources during the day: hot environmental air, direct solar radiation, and heat generation by the body (digestion, breathing, movement, etc). Of these three, two can be easily affected by management decisions in open lot systems: exposure to direct solar radiation and heat generation by the body. Shade structures can significantly reduce the amount of direct solar radiation, improving comfort and maximizing production in your herd.
Humidity plays a role by affecting how easily cattle can get rid of heat energy to the environment through panting and sweating. The higher the humidity, the more difficult it is for the animal to stay cool, and the more important it is to limit solar heat gains.
Types of Open-Wall Shade Structures
- Pole type structure with solid roof
($3+/square ft of shade) Solar radiation can be decreased nearly 100% by a structure with a solid roof. Solid roof (steel) structures are usually permanent and must be designed with snow and wind loads in mind. An important consideration is the ability to clean effectively under a permanent structure. Make sure that you are able to get your skid-steer or tractor into and out of the building.
- Pole type structure with shade cloth or snow fence
($1-3/square ft of shade) Permanent posts can be placed in the pen and cables run parallel to each other, from post to post, can support either shade cloth or snow fence material to partially block solar radiation (from 30-80% depending on material). The poles should stand at a minimum of 10 ft tall and the shade cloth should remain at a height of 8 ft at the lowest point. The cables and shade cloth can be made to be removable to allow for appropriate pen cleaning and winter storage.
- Mobile shade structures
($1.50+/square ft of shade) Several mobile commercial shade structures are available from numerous companies and can be considered especially if not many animals are housed in an area. Mobile structures can also be constructed on-site and can utilize either wood or metal framing on skids to allow for ease of movement.
Trees, if available, are a time tested shade structure. If they can be incorporated into an open dry lot is a question of creative fencing and patience if planting a stand is of interest. Oak trees, ponderosa pine, and cherry trees should all be avoided as they can be toxic to cattle.
Shade recommendations in the literature range from 20 square feet per animal to 48 square feet. That means for a pen of 100 the structure should be from 2000-4800 square feet to be effective. Finding a size that works for your situation will be important in deciding if and how to supply adequate relief from the sun.
Placement of Structures
Structures should be placed in the center of the pen, or over the center (east to west) of the southernmost fenceline. These locations allow for shade to be present in the pen for the whole day as the sun courses from east to west. Avoid placing the structure N→S on an eastern or western fence as the cattle will be unable to reach the shade for half of the day.
And of course, always provide enough water. At higher temperatures water consumption is critically important to maintain appropriate body temperature through panting and sweating.
There are other management decisions that can reduce heat stress as well. For example, timely feeding of 70% of the daily ration in the late afternoon can significantly reduce the maximal heat load by transitioning the time of maximum metabolic heat production to the cooler evening period. My colleague Warren Rusche does a good job of explaining how to prepare to minimize heat stress. If you are interested in constructing a shade structure or have any structure related questions don’t hesitate to contact me at 605.688.5672.