Cold weather increases the nutrient requirements of beef cows, particularly energy. A common question during winter storms is: How much extra supplement is needed to get cows through these weather events?
Let’s consider a 1,200-lb pregnant beef cow in the third trimester consuming prairie grass hay that is 90% dry matter (DM), 7% crude protein (CP), and 56% total digestible nutrients (TDN). Under normal conditions, this cow requires approximately 1.85 lb of CP and 12.5 lb of TDN (DM basis) per day. She would be expected to consume about 24 lb of hay daily (1.8% of body weight on a DM basis).
In normal weather, feeding 24 lb of this hay plus 2 lb of a 20% protein range cube will meet the cow’s CP and TDN requirements. However, as temperatures drop below the cow’s lower critical temperature (LCT), energy requirements increase by approximately 1% for every degree below the LCT.
For a cow in good body condition (BCS 5) with a thick winter hair coat, the LCT is about 32°F. When temperatures fall to 20°F, her energy requirement increases by about 12%, raising her TDN requirement from 12.5 to roughly 14.0 lb per day. As additional supplement is fed, hay intake typically declines. To meet this energy shortfall, she would require approximately 3 additional pounds of range cubes per day, for a total of about 5 lb of cubes daily.
The situation becomes more critical for a thin cow (BCS 4) with a thin hair coat. These cows already need to gain body condition to improve the likelihood of rebreeding, so they may already be receiving around 4 lb of cubes per day. Their LCT is closer to 40°F. When temperatures drop to 20°F, energy requirements increase by about 20%, raising TDN needs from approximately 13.3 to 16.0 lb per day. This results in an energy deficiency of about 2.7 lb of TDN per day. To offset this deficit and prevent further body condition loss, approximately 7 additional pounds of cubes would be required, for a total of about 11 lb of supplement per day. Feeding this level of supplement is both expensive and difficult to manage.
Some of this energy deficiency can be offset by providing higher-quality hay during winter storms. However, these examples clearly illustrate the importance of maintaining cows in good body condition before severe winter weather occurs.
Producers are encouraged to contact their local Cooperative Extension office for assistance in developing a winter feeding program tailored to their cow herd.
Paul Beck discussed management of cattle in cold weather on SunUpTV from February 6, 2021 https://video.okstate.edu/media/Cattle%20%26%20Cold%20Weather%20(2_6_21)/1_vca5rntt and February 20, 2021 https://video.okstate.edu/media/Cattle+%26+Extreme+Cold+%2802+20+21%29/1_83wk2akr .
