Last weekend, we welcomed the first official days of summer with the summer solstice. As temperatures rise, have you ever wondered how cattle handle long days in the heat? Today on the blog, we explore this with an excerpt from Homestead Cows: The Complete Guide To Raising Healthy, Happy, Cattle on how cattle handle the heat.
Excerpt from the Book
There are four primary ways cattle can reduce body temperature: convection, conduction, evaporation, and radiation.
Convection happens when air moves across the animal, breaking up the layer of air entrapped by the hair coat. A good breeze or a high-speed fan can increase convective heat loss. Conduction is from contact with a cooler surface or substance. Cattle standing in ponds are dissipating heat from their lower legs and hooves into the cooler water. This will also happen when they lie on cooler ground, in the shade. Evaporation happens as moisture dissipates into the air, as from sweat or from panting. Radiation is the direct transmission of heat from warmer to cooler objects in an environment. Cattle do not lose much heat by radiation on a summer day but they certainly need to be protected from the radiant heat of the sun.
As cattle move from the sun into shaded areas, the amount of solar radiation input can be reduced by as much as 50%. Shade is especially important for black-coated cows, as they absorb more solar radiation than light-colored cows. On the other hand, black cows will more effectively radiate heat at night.
Cattle will congregate under shade trees in the summer to get out of the sun. This is good from the point of reducing their radiant heat load, but it also means that they are standing close together and unable to lose as much heat, because everyone is radiating heat. There should be enough shade available for them to spread out. It is also important in summer to keep fly control measures in place. Cattle will bunch together to swat each other’s flies, and this limits their willingness to spread out.
For conduction, convection, and radiation to be effective, the air temperature must be cooler than the cow’s body temperature, normally 101°F (38°C). If the air temperature is higher, then evaporation is the only method of heat loss. And on days when the humidity level is high, evaporation quickly loses its effectiveness.
Cattle can sweat at only about 10% of the capacity that we can. They have minimal sweat glands throughout their hides, and sweat mostly through their noses. Therefore, as it gets warmer, they must pant to exchange heat with the environment. As the environment becomes hotter, they will shift to an open mouth panting. The respiration rate goes down a bit overall, but the energy required to maintain this deeper panting is much greater. A cow that is open mouth panting is stressed and needs to be cooled right away. Signs of heat stress include:
- Uncoordinated movements
- Trembling Holding head up to breathe deeply
- Elevated respiratory rate
- Loss of appetite
Should you find a cow in heat stress, move her to shade if she is not already. Cool her by running water over her legs and, if possible, set up a fan to help both with evaporation and pulling heat away from her body. Give her cool water to drink. Body type and composition affect how much heat a cow’s body retains. A smaller-bodied cow, such as a Pineywoods, is much better able to lose heat than a bigger, blockier commercial cow. They can dissipate more heat because it takes less work for the heat to make it to the outside. Something that is thick and square will retain more heat than something thin and narrow.
Lactating animals, young animals, and animals that have respiratory problems are also more prone to heat stress.
With an approach built around investing for the long term, Homestead Cows prepares homesteaders and small farmers to open the farm gate to cattle, whether a single milk cow or a small beef herd.