Sizing and Siting a Shade Structure
With winter reluctantly fading in the rear-view mirror, those hot days of late spring and summer are not very far off for cattle operations here in the Central Plains. It’s certainly not too soon to take another look at the role that shade can play in limiting heat stress in cattle. Consider the recently published findings of two studies overseen by Dr. Terry Mader (now retired UNL feedlot environment extension specialist). In one study, out of four potential measures, the temperature-humidity index adjusted by solar radiation and wind speed (THIadj) and THI estimated using pen surface temperature (THIPST) proved to be practical tools for predicting animal wellbeing1. The other study highlighted that pen surface temperature can be used to predict daily water intake and tympanic temperature in feedlot steers2. For animals in confined settings, shade helps to reduce both the direct solar heat load that cattle experience [when they are under the shade] as well as the indirect solar load [when they return to a shaded area instead of an area where the pen surface has been heated by the sun]. This article addresses two early aspects of planning for shade: how much shade to provide and how to situate shade within an open pen.
The amount of shade provided should optimize the anticipated benefits against the expected costs. Typically, the recommended amount of shade to provide is based upon the head of feeder cattle in a feedlot pen. Since not all situations on cattle operations fit neatly in the same category, some discussion is provided across a range of situations that might exist.
15 ft2/hd: Minimum size for temporary need
Holding pens and some handling areas will typically be stocked at around 15 sq. ft. per head of adult animal capacity. In these situations, a lot of body heat is being generated in a comparatively small space and the animals may be under other stresses related to handling. Provision of shade helps reduce their overall heat load. When such an area is used extensively, it often pays to have a permanent roof or shade structure in place.
In normal pen settings, however, where voluntary access to shade is offered, this low-cost size of shade (15 ft2/hd) may prove inadequate even though, in theory, all the cattle in a pen could fit under the shade. In practice, lack of space to move around within the shaded area and presence of dominant animals likely will result in some cattle being denied access to shade while others get trapped inside the crowd [with less access to fresh air and water]. The animals most likely to be denied access to or from the shaded space are often also those with greater needs (lameness, lingering respiratory issues, early stages of heat stress, etc.). Therefore, 15 ft2/hd of shade is suggested only for temporary settings or emergency situations.
20-25 ft2/hd: Common size for voluntary use within a feedlot pen
To allow cattle desired access to and from the shaded area, provision of at least 20 sq. ft. of shade per head is recommended. Anecdotally, this appears to be the most specified size and utilized range being implemented in Nebraska feedyards. As reference, this space allowance aligns with that provided in most slatted-floor beef barns. When cattle approach market weight, there is just enough room for animals to maneuver within the space (or lie down) without being able to see much of the pen floor.
25-30 ft2/hd: Suggested size for high-risk feedlot cattle
In terms of heat stress, ‘high-risk cattle’ includes not only those animals having underlying health issues or experienced other forms of stress, but also those cattle that are above traditional market weight, especially if they are dark-hided and/or fed a hot ration. It can be unsettling to consider that otherwise healthy cattle are most susceptible to heat stress just before being marketed, after most of their production costs have been incurred. The risk of cattle death loss to heat stress is probably the main driver now for installing shade and is expected to become even more of a concern if finish weights continue to increase and weather extremes trend toward being more severe. Provision of more shade in pens having high-risk cattle will help accommodate their additional needs and reduce the risk of death losses, which can help justify the expense.
35+ ft2/hd: Special situations
As shades are made larger, structural and logistical issues also grow, which reduces the cost-competitiveness of providing more-spacious amounts of shade in most outdoor settings. Special needs areas, such as sick pens, maternity pens in a confined-cow operation, and some limited space for new cow-calf pairs where summer calving occurs might be examples of where more shade could be justified. In a building, 100 sq. ft. or more of pen space per head would be needed for these animals, so providing a third to half that amount of shade in an outdoor setting could still be a cost-effective way to accommodate smaller numbers of animals resting comfortably under shade.
Otherwise, it becomes challenging to justify providing large amounts of shade, especially when compared to confinement buildings that can capture other benefits for managing animals and manure.
How to situate shade within an outdoor pen depends on several factors, with primary considerations being pen layout, drainage, and orientation.
Pen layout: As a priority, the shade structure or structures needs to function with, not against, the pen design when it comes to animals being able and encouraged to move freely between water, feeding and resting areas. While cattle will often prefer to stand (rather than lie down) under shade during hot weather, the shade still needs to accommodate the well-being of resting cattle, so shade should be prioritized for the resting area.
For the typical rectangular pen and a rectangular shade, the long dimension of the shade should align with or parallel to pen dividing fences. For circular or square shade, this is less of a consideration. Since mounds are utilized in many open pens for all-weather rest areas, and the pen layout considerations are similar, shades frequently are placed over the mounds.
Pen drainage: Proper pen design builds drainage into the layout. In a lot of real situations, though, the existing site or layout presents potential challenges to maintaining good drainage, and adding shade to a pen can exacerbate the risk. The key thing to keep in mind is that shaded areas will likely experience concentrated animal density, which can lead to erosion and formation of ridges around the perimeter of the shaded area. As much as possible, locate the shade structure to encourage runoff to flow away from and around the shaded area.
Orientation: The orientation of a shade structure makes a difference, although ensuring properly functioning pen layout and drainage are usually greater priorities. When shade is oriented east-west, the area below the shade material is shaded for a longer portion of the day. Benefits of an E-W orientation include cattle can usually find shade without moving as much, and there may be better exposure to summertime breezes (assuming southerly prevailing winds). The main disadvantage is that the area under the shade material is more likely to develop into a mudhole. For these reasons, an E-W orientation is preferred for cattle barns and other situations where animals are confined to the area below the roof and this area has a concrete floor. When a shade structure is oriented north-south, the shadow will move from west to east over the course of the daylight hours and cattle will need to move periodically to stay in shade. As a result, foot traffic and manure will be dispersed across the pen, and the entire pen will have some exposure to sunlight, which should help slow down mud development. In an open dirt lot, a N-S orientation is advantageous, other factors being equal.
For additional information on managing cattle in hot weather refer to: https://beef.unl.edu/beefwatch/.
Interviews with the authors of BeefWatch newsletter articles become available throughout the month of publication and are accessible at https://go.unl.edu/podcast. You can subscribe to the BeefWatch newsletter here: http://go.unl.edu/Beefwatch_subscribe
1Arias, R.A.; Mader, T.L. Evaluation of Four Thermal Comfort Indices and Their Relationship with Physiological Variables in Feedlot Cattle. Animals 2023, 13, 1169. https://doi.org/10.3390/ani13071169
2Arias, R.A.; Mader, T.L. Pen Surface Temperature as a Predictor of Daily Water Intake and Tympanic Temperature in Steers Finished in Feedlots. Animals 2023, 13, 1150. https://doi.org/10.3390/ani13071150