Pens that provide shade can help cattle keep body temperatures within safe zones. "Shade is extremely important in an environment without much cloud cover," says Don Spiers, Associate Professor of Animal Science, University of Missouri, Columbia. "If using a roof, it should be insulated, especially if it's metal. Otherwise you'll get radiant heating and it will be like an oven underneath. The roof should be at least 10 feet off the ground. The higher the better, to allow more air movement beneath it," says Spiers.

Studies looking at effects of shade were done at Texas Tech University in 1999 and 2000. Mike Gaylean, Department of Animal Science, says the studies compared shade to no shade, and to use of sprinklers for cooling the cattle, and found that shade was more effective than sprinklers.

"Feedlot people in many regions feel shade won't pay for itself, causing problems with drying and cleaning the pens; the structures would be in the way. They don't want to put something up that they'd have to take back down. In Arizona, California, and other southern climates where shade is used in feedlots, this isn't a problem; it's so dry they don't have trouble with moisture--they don't take them down in the winter," says Gaylean.

"We did behavioral observations, measurements of dust, and looked at behaviors that generate dust. The pen surface under the shade gets much wetter (because the animals stay there) and the activity of the animals changes because they stay in the shade all day. So dust generation is less. In our area we have a huge problem with dust because it's so dry. Shade may be one way to reduce this, minimizing two problems at once," says Gaylean.

Australian Research      Advantages were seen with shade structures that are reflective (light colored) on the top surface, absorptive (dark colored) on the bottom, and constructed to allow airflow through the structure. Air movement under a structure is affected by its size (height and width), slope of the roof, and the ease with which air can move through it. Shade cloth has an advantage over a solid roof; air passes through the material.      Solar radiation causes air directly under the roof to become hotter than the surrounding air, and it rises. This air "buoyancy" can be used to create air movement beneath the roof, by allowing hot air to slide upward on the inside of a sloping roof. As this air moves up, it drags air in from the sides. The rate of movement depends on the slope of the roof, and roughness of the material. A slope of 18 degrees works well on a small structure, and 10 to 15 degrees of slope has a similar effect in larger structures.      Heavy duty shade cloths allow wind and rain to pass through. Lightness and pervious nature of shade cloth give it advantages in design efficiency over tin. Shade should be 15 feet high or more to allow enough air movement, according to the Australian research. In the afternoon there's an increase in shaded area (due to angle of the sun). Because the roof is high and pitched, the shade moves across the pen quickly. Shade that gives the largest area per animal is most important in late afternoon, when cattle have been accumulating heat the longest and daytime temperatures are highest.      Care should be taken to place structures so shade stays within the pen in the afternoon. Researchers also recommend that shade not be placed at the water troughs since this is an area where moisture accumulates--to prevent buildup of wet manure. To limit moisture buildup (and humidity and ammonia levels), the roof should be high. This not only allows more air movement but also exposes more of the ground surface to drying--from more access to morning and mid-day sun and from greater movement of the shaded area, which reduces occurrence of shade-related wet pen conditions.

"Our shade structures had solid galvanized metal roofs, mounted on steel pipes, with some slope (13 feet high on the north, 12 feet high on the south), similar to what dairies have here. In other regions, people might use snow fences or some other material. We tried to provide two square meters of shade per animal." Orientation of the shade was east to west, 120 feet long, 16 feet wide.

"In the small pens (first study) we used black, light-occluding cloth. It blocks out 80 percent of the light and is very effective. If you can devise a system that won't blow away, this would be very portable, because you can roll it up," explains Gaylean. A PVC structure was built to cover 2/3 of the pen area.

"In the two years we used shade, those cattle had a six percent improvement in average daily gain, and a three percent improvement in feed conversion, along with increase in feed intake. All you are doing with shade is alleviating the effect of heat stress on feed intake, allowing the animals to gain better," he says.

At the end of the first study, the shaded heifers weighed 59 pounds more than unshaded heifers, dry matter intake was seven percent more and average daily gain was 11.8 percent higher. Hot carcass weight of shaded heifers was 35 pounds greater, fat thickness was higher, and there were no dark cutters (compared with 21.1 percent in unshaded pens). Results in the next study were similar. Shaded cattle showed only half as many dark cutters, and twice as many Choice carcasses, compared with their unshaded peers. Aggressive behavior was more than four times higher in unshaded heifers.

"We used yearling heifers on feed for 130 to 150 days, starting them on feed in May or June. If started on feed later in the summer, I suspect they would be able to compensate, and the overall effect of shade might be less. After it cools down, the unshaded animals compensate quite a bit. But if started on feed early, they can't ever fully compensate," says Gaylean.

There is also much less risk for severe heat stress. During a heat wave in the Midwest in 1995, more than 4000 cattle died, causing a direct loss of $2.8 million, with an additional $25.2 million cost in decreased performance. ©