Producer Question
Q. How do a cow's energy requirements change with cold weather? How much more feed does she need?
A. Moisture, high winds, and cold temperatures all increase the cow's energy requirements. Cows in an optimal body condition score (BCS 5 to 6) are better able to withstand adverse environmental conditions than thin cows. The lower critical temperature of a beef cow is the lowest temperature a cow can be exposed to before she needs to have changes metabolically to help her cope with cold stress.
Lower critical temperature for beef cows is influenced by hair coat condition (dry or wet/muddy), body condition (thin, moderate, fleshy) and hair coat description heavy/winter, winter, fall, or summer. As hair coat changes from summer to winter, BCS changes from thin to fleshy, and hair coat changes from dry to wet, lower critical temperature decreases which means cows can withstand harsher conditions without an increase in energy needs. Magnitude of coldness is equal to Lower Critical Temperature - Wind Chill Index. Energy requirement increase about 1% for each degree of cold stress. As an example, cows that have a heavy winter hair coat that is dry and are in condition score of 5 have a lower critical temperature of 19°F.
Be very careful if you plan to use grains (corn) to increase the energy density of the diet during severe condition as you may do more harm than good. Feeding more than 2-3 lb/hd/day of corn to cows on a forage based diet will decrease fiber digestion. When cows are on a forage-based diet and supplemental energy is needed, consider the use of high energy, non-starch feed stuffs such as distillers grains and soy hulls to meet cow energy requirements. It would not be advisable to change rations daily, but if is predicted that weather conditions will be severe over a period of time then ration changes may be warranted.
A webinar titled Caring for Cattle in Cold Weather highlights the effects of cold weather on cattle and management practices to help mitigate these effects.
Rick Rasby
UNL Beef Extension Specialist
University of Nebraska