Cold Stress and Beef Cattle
Figure 1. Effective temperature chart for mature cows; Adapted from John Herrick, Iowa State University, Extension Veterinarian
When winter weather arrives, we need to be prepared to handle and transport cattle appropriately. The heat of summer can be a challenge, but the cold, wet, and windy conditions of winter and early spring can cause headaches that are unmatched.
Winter stress factors may include temperature, wind, rain, snow, mud, feed quality, feed quantity, body condition, adaptation, and perhaps others. Cattle can be remarkably tolerant of cold conditions, but there are certain times when managers need to consider measures to mitigate the stress caused by cold conditions. This requires some knowledge of the science involved, as well as a certain amount of common sense and experience.
Research refers to the lower critical temperature (LCT), which describes the ability of cattle to withstand cold conditions. The LCT is the temperature at which maintenance requirements increase to the point where animal performance is negatively affected. Various sources report this temperature to be between 18 and 20°F. However, a fact sheet from NDSU states that after adaptation, mature beef cows in good body condition during the middle third of gestation may have an LCT as low as minus 6°F during dry, calm conditions.
Critical temperatures for beef cattle are determined in part by the condition of the coat. Below the critical temperature, livestock must expend more energy to maintain their body temperature.
| Coat Description | Critical Temperature |
|---|---|
| Summer coat or wet | 59 degrees F |
| Fall coat | 45 degrees F |
| Winter coat | 32 degrees F |
| Heavy winter coat | 18 degrees F |
Adapted from D.R. Ames, Kansas State University.
When the animal has a lighter coat, the LCT goes up. If the cow has a summer coat or is wet, the LCT is around 60°F. Of course, we wouldn't normally expect a cow with a summer coat to be subjected to winter. Early blizzards out west, where we often see a number of dead animals, adversely affect cattle whose coats are not at a winter level. Cold rains can happen in the winter, and a winter coat is almost useless when wet. When the coat is wet, it loses the insulation factor that is essentially air trapped between hair fibers. Most stockmen know that an animal is usually better off in snow rather than cold rain.
Several sources concur that for every degree below the LCT, a cow's energy (TDN) intake increases by one percent. Basically, the animal requires more energy to maintain itself.
What can a cattle manager do to make sure their animals are not subjected to unnecessary cold stress?
Protection from wind is obvious. Wind chill can worsen stress caused by cold rain. A well-ventilated building, a stack of big bales, woods, brush, fencerows, and hollows are all potential windbreaks.
Reduce muddy conditions to every extent possible. This can be difficult, especially in March. Mud has pretty much the same effect as rain in reducing insulation from the cattle's hair. Use bedding to help keep cattle clean and to provide insulation from mud or frozen ground. Rotate hay feeding areas if possible. In many situations, mud can't be entirely avoided, but at least try to establish an area where cattle can lie down in a dry, bedded area. If you need assistance with mitigating muddy, heavy-use areas, you can contact the USDA-NRCS to discuss ideas on methods to improve your situation.
Feeding programs may need to be tweaked in prolonged cold conditions. Be prepared for cattle to eat more: cows typically consume 2.5% of their body weight in hay, but this may increase to 3.5% of their body weight. Provide higher-quality forage if available. Digestibility and energy levels in the forage are the key things to focus on. Higher-energy forage will help the cattle cope with increased energy expenditure.
Supplementing cattle with grain or by-products is another strategy, especially if the only forage available is low quality. A few pounds of grain may be all it takes, but consult a nutritionist to ensure you don't overfeed or underfeed the supplement.
One area of concern that we often overlook is transporting animals in cold weather. The chart in Figure 1 illustrates the effect of wind speed on temperature. There may be no wind, but the animals on your trailer, heading off to the stockyards or starting a three-hour drive to Harrisburg for the PA Farm Show, only know that your truck is moving at 60 miles per hour, and it's really cold back there in the trailer.
Looking at the chart, if the temperature is 20°F and the wind speed is 40 mph, the wind chill is -21°F. If you haven't done something to block the airflow in your trailer, those animals are having a pretty chilly ride.
Remember, if your cattle are wet and you are transporting them in cold weather, the danger will be even greater. It will be critical to get your animals to the destination as quickly as possible.
Cold weather is stressful for both cattle and cattle producers. The use of a little common sense and planning will go a long way to make this winter a less stressful time.
