Effect of Cold Weather on Feed Requirements
     Research in Western Canada, Kansas and elsewhere has shown that the stress of extremely cold weather increases the energy requirements of cattle. This can be an important consideration in the wintering of brood cows in the Northern states. The requirements listed in the tables here are valid for a temperature range of 30° to 80° F which is normally considered the comfort zone for most cattle. Energy requirements increase when the temperature goes above or below this range. The increase is especially dramatic for cattle in extremely cold weather with no shelter. Wind, together with cold stress, further increases the need for additional energy to maintain body temperature and body weight. Wind chill factors for beef cattle are given in the following table:

     Generally speaking, an 1100-lb. dry brood cow in good condition with a full coat of winter hair and no access to shelter will require 13 % more energy or TDN for each 10° decline in the wind chill factor below 30°. For example, if the temperature were 0°F and the wind velocity were 20 mph, the wind chill factor would be -20°, or 50° below the critical temperature of 30°. This means that her maintenance requirement for energy would be increased by 65 %. According to Table 3, an 1100-lb. cow in mid-pregnancy needs 8.6 lb. TDN daily if she is in the comfort zone of 30° to 80°F; therefore, her TDN requirement would be 8.6 x 1.65 = 14.2 lb., or an increase of 5.6 lb. of TDN. If the dry matter in the hay she receives averages 50% TDN, this would require the feeding of 28.4 lb. hay DM, which slightly exceeds her expected maximum daily DM intake of 26 lb. However, cattle consume more DM during cold weather so she would likely meet her requirement. If the wind chill factor were to drop significantly lower, a higher energy feed such as corn silage or grain would probably have to replace some of the hay in order to maintain her body weight. If the wind chill factor fell to -66°, her daily TDN requirement would be increased by 125% or 10.7 lb. This amount added to 8.6 lb. would come to a total of 19.3 lb. TDN or 38.6 lb. of hay dry matter. At this point. she could not consume enough hay to maintain her body weight.

     An extremely thin cow with a poor haircoat is stressed even further by cold weather. Her energy requirement increases by about 30% with every 10° drop in wind chill factor below 30°F. On the other hand, cattle on feed are not stressed as much by low temperatures; their TDN needs are increased by about 8% for every 10° decline in wind chill factor below 30°F.

     When using the requirements listed in the tables that follow, allowances should be made for cattle that are under extreme cold stress for extended periods of time with no access to shelter or windbreak. One or two days of cold stress are no cause for alarm, but long periods of below zero weather should be accounted for when feeding the cow herd.

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