It’s no secret that winter weather and associated wind chill increases the amount of dietary energy needed for cows to maintain body condition. The traditional rule of thumb is that for every degree (actual or wind chill) drop in temperature from a storm front, producers need to increase daily energy delivery by 1 percent for cows in a body condition score (BCS) of 5 or 6.
While this may not need to be sustained for extended periods of time, implementation of extra supplement for a few days around the cold front is recommended until cattle become readjusted to the colder temperatures.
Often overlooked, however, is the added energy that thin (less than BCS of 5) or wet cows need in order to maintain body condition in the same frigid environment. In most circumstances, those thin or wet cows need 2 to 3 percent (as opposed to 1 percent) more daily dietary energy to maintain body condition.
While producers often note slightly increased forage intake as weather turns for the worse, the ability of cattle to ingest enough added forage to meet these requirements is unlikely, if not impossible, depending on the extremeness of weather conditions.
More important to producers, however, is not how much more energy a cow needs, but how this requirement relates to pounds of feed fed.
Example rations have been developed with the Iowa State University Beef Ration and Nutrition Decision Software (BRaNDS, a ration-balancing program) to illustrate how lower temperatures and BCS impact feed requirements for 1,350-pound cows in their third trimester of gestation (Table 1).
Keep in mind, however, these are just examples. Therefore, consult with the team of experts you have assembled, including your nutritionist and beef extension specialist, when developing rations for adverse weather conditions. 
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Patrick Gunn
- Assistant Professor of Animal Science
- Iowa State University
- Email Patrick Gunn
