Cold stress and dehydration can impact cattle health
Published on Feb. 8, 2020
Cattle are very adaptable and can thrive in many different climates. Some are better adapted than others, however, to handle heat or cold. Breeds in North America are usually chosen for the climate in which they live, whether it’s the hot, humid environment of Gulf States or the bitter winters in the northern Rockies or plains.
They need a chance to adjust to seasonal changes, however. For winter, they grow a longer, thicker hair coat.
The hair and a layer of fat under the hide provide insulation to reduce heat loss from the body. Changing temperatures in the fall and shorter days stimulate growth of winter hair.
As days get shorter and weather is colder, body metabolism changes. Feed intake increases and passage of feed through the digestive tract speeds up. Feed requirements for cattle may go up as much as 10 to 25 percent. All of these changes contribute to an increase in heat production so the animal can withstand winter temperatures.
In order to process the additional feed, the digestive tract needs adequate fluid. A cow’s water requirements are not as high in winter as in the heat of summer or during lactation, but she needs to drink enough water to handle the demands of ruminant digestion and increased metabolism, to prevent dehydration and impaction.
It is important to provide adequate water for livestock during cold weather.
Julie Walker, beef specialist at South Dakota State University, says if cattle don’t have water, they are not going to eat. If they don’t eat enough, they don’t have the fuel to stay warm.
“Fermentation in the rumen generates heat and helps alleviate cold stress,” she says.
Factors that affect ability to handle cold
Cattle can tolerate colder temperatures with a dry hair coat.
“As long as their heavy winter coat is dry, they are comfortable at lower temperatures than if the hair is wet. They do best if they have a chance to grow a good hair coat before extremely cold weather. If it’s a gradual change, they can deal with it much better than when we have an early blizzard,” says Walker.
“The rule of thumb is that for every one-degree Fahrenheit below a cow’s lower critical temperature she requires an increase of one percent in feed to keep warm – if she has her winter hair coat,” says Walker. “Typically, if she has a dry coat, the critical temperature is about 19 degrees Fahrenheit. If she has a wet coat, losing its insulating quality, that critical temperature goes up to about 60 degrees Fahrenheit.”
Feed intake must increase to generate enough body heat.
“In the range from 23 to 41 degrees Fahrenheit, the increase would be three to eight percent. If the temperature range is between five degrees and 23 degrees, we’re looking at a five to 10 percent increase in feed. If the temperature is lower than five degrees, it would be eight to 25 percent increase,” says Walker.
She continues, “It just depends on how cold it gets and whether cattle have protection from wind, since wind chill effectively lowers the temperature that these animals can handle.”
“Wind protection can greatly reduce the impact of cold. It also helps if we can provide bedding in some situations, so they are not lying on frozen ground and suffering more heat loss. To reduce cold stress there are several things we can do to reduce heat loss and increase the amount of heat produced by the animal, via feed. Fermentation of forage is an excellent source of heat production,” says Walker.
Having cows in adequate body condition before they go into winter is important.
“This helps them handle the cold much better than if they are thin, with very little fat covering,” says Walker. “The impact of cold is totally different for a cow in a body condition score of three compared to one with a condition score of six.”
The additional body condition not only serves as insulation but also provides some reserves of energy to draw from for heat production when temperatures drop.
Importance of water
Cattle always need water, and the more they eat, the more they must drink in order to process the feed.
“It’s crucial to keep water sources open, not covered with ice, and make sure they have an adequate supply of water. We know cows can eat snow, but it can’t be crusted over and some cows don’t eat snow as readily as others. We don’t know how to teach cows to eat snow,” she says.
They generally learn to eat snow by mimicking other cows, or their mothers, if calves are wintering with their mothers. If we simply put a herd of cows out on winter pasture and they are not accustomed to eating snow, many are slow to learn. We can’t depend on having cattle utilize snow for moisture.
“They should always have a water source. Some cows may not come to it every day if they choose to stay out and graze and lick snow, but it’s there when they want it, Walker says.
“Some cows will only come in for water every other day or so because snow consumption provides much of what they need. Research has shown that water consumption is around six gallons per day for pregnant dry cows at 40 degrees Fahrenheit. However, we don’t know how much water they actually need in these situations with snow providing part of the fluid requirement of cows, because we can’t replicate nature in a research study. We just know that cows need adequate water – via snow or some other source – to prevent dehydration,” says Walker.
It is very important to monitor cows and their water sources through winter, and know if they are drinking enough and eating enough, and maintaining adequate body condition.
Heather Smith-Thomas is a corresponding writer for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
