By Cheryl Anderson
DTN Staff Reporter
OMAHA (DTN) -- Cold weather is hard on all livestock, but can be especially challenging for pregnant cows in their third trimester.
Cows require more energy in winter to stay warm and to maintain their core body temperature during prolonged periods of cold, according to Justin Waggoner, research and extension beef systems specialist at Kansas State University.
Energy is especially important for spring-calving herds with cows well into their third trimester and calving in late January/early February.
"Nutrient requirements for cows are steadily increasing as we go through the third trimester and calving, when you add on top of that a cold stress also increases energy needs," Waggoner said.
Waggoner explained cattle are the most comfortable in what is called their "thermo-neutral zone." This is when cattle are not exposed to either cold stress or heat stress and don't have to expend any energy to stay warm or cool off. That zone does vary somewhat based on factors such as air temperature, cover and moisture.
For a cow in good body conditions, cold weather increases energy requirements in cattle by 1% for each degree below the lower critical temperature. Waggoner explained the lower critical temperature for cattle can vary due to body condition or how heavy their coat is.
Estimated Lower Critical Temperature for Beef Cattle
| Coat Condition | Critical Temperature (degrees F) |
| Wet or summer coat | 59 |
| Dry, fall coat | 45 |
| Dry, winter coat | 32 |
| Dry, heavy winter coat | 18 |
(Chart courtesy of Justin Waggoner, KSU)
A good rule of thumb is to be concerned whenever the high for the day is 32 degrees Fahrenheit or lower, as that is when cattle with a dry winter coat can begin experiencing cold stress. Cattle with heavier, more developed winter coats can tolerate temperatures even lower, somewhere around 18 degrees, before they experience cold stress.
Although temperature, wind chill and humidity all play a role in adding to cold stress, Waggoner emphasized probably the biggest factor is whether the animal's coats are wet or dry. A wet coat loses its insulating properties and its ability to trap air, so cattle lose their body heat faster and are less able to keep warm.
"The lower critical temperature is actually only about 59 degree if cattle have a wet coat, which seems like a fairly warm temperature," he explained. "But if cattle have a dry coat, that number is probably closer to about 18 degrees. If you look at some of the temperatures and wind chills we've had recently, we've probably been below that number throughout a fair chunk of the Midwest."
Wind is also a big factor that can exacerbate cold stress, so any kind of cover or windbreak can also help keep cattle warm. Waggoner said there are a number of options for providing windbreaks, including some commercially available portable windbreaks.
Other times cattle producers can be fairly creative in providing windbreaks, such as placing stacks of hay in strategic locations, but outside of fences, to offer some form of protection.
Although most cattle can withstand one or two days of cold weather fairly well, longer durations below that lower critical temperature should raise concern. Waggoner explained that during cold weather, cattle tend to not go out and graze as much, and tend to congregate in areas where they have protection.
He added that during prolonged periods of cold, producers need to be aware of how much time cattle are spending grazing and how to respond with supplements to ensure their nutrient requirements are met.
INCREASING ENERGY
While cattle do require additional energy in their diets during cold weather, it does not necessarily mean they need more protein or minerals. In fact, Waggoner said cold stress only increases energy requirements, not protein requirements.
When cows are in their third trimester and start to calve, both protein and energy requirements increase. Typically cows are supplemented with additional protein during the winter months to improve the use of dormant forages such as native grass or stalks. The additional protein provided increases both forage intake and utilization.
"So when we have a cold winter event, some producers just offer more of a protein supplement. That does provide some additional energy, but they are probably over-feeding the protein," he said.
Producers should have a strategy to balance resources with the increased nutrient requirements of spring calving cow herds during cold weather events, Waggoner said.
Most operations have forage of various nutrient qualities in their hay inventory. As winter progresses into calving season, cold weather is a good time to strategically use forages that are of relatively higher quality.
"There are a variety of approaches one can take, from providing higher quality forage or putting out small amounts of grain," he said. "It really depends on what's available."
Ethanol co-products such as dried distillers grains also work well to supplement energy, as they do provide a fair amount of both energy and protein, Waggoner added.
All in all, producers need to plan and take in account cold weather for spring calving herds.
"Mother Nature can really throw some stuff at us this time of year," he said. "These weather patterns really add to challenges that cows are already facing nutritionally in cold weather."
Cheryl Anderson can be reached at cheryl.anderson@dtn.com
(CZ/SK)
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