Heat stress in feedlot cattle leads to serious animal-welfare and economic implications. Documented feedlot cattle losses show more than 5,000 head have died as a result in seven of the last 20 years, and non-death costs are estimated at five to 10 times greater than death losses.
Environmental conditions, including temperature, humidity, wind and solar radiation, can affect heat load. Those environmental and animal factors are difficult to control, especially cost-effectively. However, it’s possible to reduce the impact. When a light wave strikes a surface, it can pass through, be reflected away from the surface or be absorbed and converted to heat. As the amount of light that is reflected increases, the amount absorbed decreases. That fact accounts for the reason white-roofed buildings and light-colored cattle are cooler.
Because about 75 percent of domestic beef cattle are black, this research study asked: Could a reflective pigment on the hide reflect solar energy and help reduce heat stress?
The pigment, titanium dioxide, reflects light, doesn’t react chemically and is approved for use in feeds, food coloring and sunscreens. Researchers applied the pigment to 30 feedlot heifers—29 black and one red—weighing on average 591 lb. within a range of about 61 lb.
Heifers were randomly assigned to either control or coated treatments. The coating was applied to the back with an electronic airless sprayer. The area over the shoulders was left uncoated to serve as a control. Vaginal thermometers attached to blank controlled internal drug-release devices, or CIDRs, continuously recorded their internal body temperature.
The researchers applied coatings and thermometers between 10 a.m. and 11 a.m. on a day with a high temperature of 101°F and a temperature/humidity index of 87.8. Starting at about 1 p.m., they then measured reflectance using a suspended modified digital camera and hide surface temperature with a suspended infrared thermal-imaging sensor. White, black and gray panels placed nearby provided reference temperatures. Reflectance and hide surface temperature were compared between two areas of the same animal. At 2:30, severe heat stress in several cattle required researchers to turn on a sprinkler.
They found reflectance of blue, green and red light was 5.7, 8.8 and 10.3 times greater, respectively, for the animals’ coated areas than the uncoated areas. Surface temperature on the back averaged 102.3°F and 108.3°F for coated and uncoated areas, respectively.
Uncoated cattle had a 1.6°F greater body temperature increase than coated cattle over a two- to three-hour exposure to natural solar radiation, suggesting the coating reduced heat stress.
By: Elsie J. McCoy and Steve J. Bartle, Beef Cattle Institute, Kansas State University
Source: Bovine Veterinarian Online