Reducing Cattle Cold Stress
Cold winter weather reminds us all of the dangers of cold stress on warm-blooded animals like humans and cattle. Humans know adding layers of clothing will help reduce cold and limit exposures when wind speeds result in dangerous wind-chill conditions. Cattle are not so lucky. They will seek protection from wind and precipitation when it is available, but often their options are limited. Good managers can help.
The main protection cattle and other animals have from cold stress comes from the insulation provided by the hide and hair coat. When that hair coat is heavy and dry, cattle protected from wind effects may not experience a great deal of cold stress even when temperatures fall well below freezing. However, a wet or muddy matted hair coat does not provide much insulation and they can start to feel cold stress when the temperature is well above freezing. In addition, cattle exposed to wind or wind chill, further decreases the effective temperature cattle feel by increasing the rate of heat loss from the hide.
When cattle are experiencing cold stress, they try to compensate by using a higher fraction of their feed energy to produce extra body heat. This reduces energy available for gain. The combined effect on performance is increased intake along with reduced gain and feed efficiency. The effect of cold stress on energy use and performance in cattle can be modeled using formulas from the National Academies of Science publication Nutrient Requirements of Beef Cattle (NRC).
An Iowa State University Animal Industry report on cold and heat stress in cattle used reported temperature, wind and precipitation conditions from six Iowa weather stations from 2006 to 2014 to model cattle in an open lot with no wind protection. Results indicated cattle would likely be experiencing cold stress or increased energy demand according to NRC equations 18% of the time or about 65 days out of the year. In about half of those days, the actual temperature was in 20-40 degree range. If wind speed was reduced by 2/3, the percent of cold stress days drop to 10.5% and if the hair coat is assumed dry, then cold stress is almost zero except on days when actual temperature is below zero. the report is available at Effect of Shelter on Heat and Cold Stress on Feedlot Cattle in Iowa.
Wind protection, keeping cattle dry and bedding are the main ways to help mitigate cold stress and the effect on cattle performance. Bedding helps to keep cattle dry and the hair coat from becoming matted as well as providing some insulation from heat loss to cold surfaces. Many studies have shown increased cattle performance of using bedding during the winter feeding period versus no bedding. Iowa open feedlots should provide wind protection for winter feeding. Tree windbreaks, constructed windbreaks, buildings, or even stacks of bedding/hay bales can provide beneficial wind protection. For maximum cold stress relief, buildings with available roofed floor space of at least 20 square feet per head can provide both wind protection and reduce precipitation effects on hair coats. This can be especially beneficial in Iowa where winter precipitation events are often followed by strong northwest winds. Making sure roofed areas are well ventilated is important and increasing the air temperatures in the building is not needed if cattle are protected from high wind speeds and precipitation. Data from multiple upper Midwest research studies confirm the winter performance benefits of windbreaks or buildings for cattle feeding. On the coldest days, no amount of protection can completely eliminate cold stress, but protection from wind and wet hair coats can greatly reduce stress.