Extreme Weather: Extension educator highlights management for cold-stressed livestock
“Cold stress is obviously something we have fresh on our minds since we have had a lot of cold temperatures and snow across the state,” stated Micah Most, University of Wyoming (UW) Extension educator in Johnson County, during the Fremont County Farm and Ranch Days in Riverton on Feb. 9.
Since Wyoming producers have dealt with several extreme weather events over the past few months, Most discussed how producers can manage cold-stressed livestock.
Cold stress
To begin, Most explained cold stress occurs when animals are pushed outside of their thermal neutral zone, and therefore, have to increase heat production through increasing metabolism, shivering, etc.
“We can also expect to see cold stress set in when animals get wet, because it passes through their coat cover, and they lose their insulating capacity,” he said, noting producers should be especially concerned when weather conditions are wet and windy.
“I think it’s also important to note cold stress can occur outside of the winter season,” he added. “An example is an early fall freeze, which can be damaging because animals are still in their summer coat condition. This is why early fall freezes are more of a stressor than late spring freezes.”
Most also noted the importance of knowing the difference between acute stress and chronic stress. He explained acute stress occurs over a short period of time – 24 to 72 hours – while chronic stress occurs over a longer period of time – a week or more.
“Livestock can typically handle cold stress in acute form, but when it is sustained over a longer period of time, there will be some severe consequences,” he said.
He also mentioned smooth temperature transitions are much easier on livestock than quick spikes and drops in temperature.
“For instance, the same animals on a ranch that can handle the cold temperatures we have been experiencing will be just fine in the middle of summer,” Most said. “However, if we were to move directly from one to the other without a period of adjustment, there would be some severe consequences.”
“When temperatures fluctuate this quickly and extremely, animals will struggle and get really sick,” he added.
Factors affecting cold stress
In addition to fluctuating temperatures, Most noted there are several factors playing a role in whether or not animals will feel cold stress and how severe it will be.
He shared air temperature and humidity are the first factors that come to mind, although humidity isn’t much of a problem for producers in Wyoming.
“Wind speed is something we deal with a lot here, however. Wind is a form of convection, which, depending on whether it is winter or summer can either be desirable or undesirable,” he said.
There are also several nonenvironmental factors, according to Most.
These include nutritional status, body condition score (BCS), rumination, hair coat and wool condition, genetics and stage of development.
“BCS is a big one because animals need to expend energy to maintain their body temperature so they don’t fall outside of the thermal neutral zone. If they are in good BCS, they will have the energy reserves in place, and this is not an issue,” he explained.
“Additionally, ruminant livestock species are special because they have a rumen, which serves as a built in furnace. So, when temperatures get cold, microbes breaking down cellulose in the rumen help ruminants maintain their body temperature,” he continued.
When it comes to hair coat and wool, Most shared it is a good thing when animals have snow on their backs, as this proves their winter coat and fat insulation is working.
However, if producers see animals with snow melting off of their backs, Most suggests they provide shelter to help animals get warm and dry and then reevaluate their feeding program to get them into better body condition.
Managing for cold stress
Although livestock in Wyoming are more prone to experience factors causing cold stress, especially with recent weather conditions, Most said there are several ways producers can manage cold stress in their herds.
“When it gets cold, animals start shivering more to maintain their body heat. They also bunch up and do a lot more standing, which means they aren’t spending as much time laying down and ruminating,” he explained. “The consequences lead to greater feed requirements.”
Most further noted when animals are pushed outside of their thermal neutral zone, they expend energy to shiver in an effort to maintain body temperature, which subsequently translates into an increase in total digestible nutrient demand.
“If animals are out on dormant water range, their intake will be limited because they will be eating typically lower-quality forages,” he said.
Additionally, during this time, many females are nearing late-gestation, which also significantly increases energy demand.
In addition to increasing feed intake, Most also mentioned windbreaks can play a large role in keeping animals warm and dry during nasty, winter weather events.
“The best way to do this is to set up two bases at a 90 degree angle, with the point of the triangle directed into the prevailing wind,” he said. “This will form a protected area in the center, equal to five times the height of the windbreak.”
Animals fit for the environment, as far as genetics go, make managing for cold stress a lot easier as well, according to Most.
“This is an extreme example, but think about the difference between Bos indicus cattle and Scottish highland cattle,” he said. “These two animals will handle the cold a lot differently, simply based on their genetics and the environment they come from.”
He continued, “This is something to keep in mind when purchasing animals from out of state. For example, if a producer went out and bought a bunch of heifers from Texas right now, and then moved them up here in the dead of winter, there might be some consequences.”
Lastly, Most encouraged producers to offer bedding to keep animals off of the cold, hard ground.
He noted this is especially important for ruminants, so they are able to lay down, ruminate to digest their feed and maximize the nutrients they are provided, as well as for breeding males who are more apt to experience frostbite on reproductive organs.
Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
