Caring For Cattle During Cold Weather Extremes

   The extreme weather that the Midwest is experiencing is trying for everyone. Add freezing rain and snow on top of the bitterly cold temperatures and you have a recipe for a miserable time for you and your livestock. Long-range forecasts for January and February in the Midwest suggest that we will continue to experience below normal temperatures and normal precipitation.
   It is important to monitor your cattle closely during these very stressful periods. Beef cattle increase their body heat production as a response to severe cold exposure by increasing their metabolic rate (heart rate, respiration and blood flow) – increasing their maintenance requirements. Thus in response to increasing their metabolic rate, these cattle will need to consume more to meet their increased maintenance requirements. Cattle will consume 105 to 110 percent of their predicted intake when temperatures drop below 22° F and up to 125 percent of predicted intake below 5° F.
   However, during severe cold (wind chills of -20° F or lower) cattle may stop eating because they are reluctant to leave sheltered areas. Alternatively cattle may simply get too cold; heat loss and cold stress will reduce their appetite and efficiency of feed conversion since the body’s metabolism is adversely affected (mammals must maintain a constant body temperature to keep up the proper metabolic processes). Thus during winter it is important to provide highly digestible feeds – higher quality forages – so that cattle can compensate for their increased energy needs resulting from increased maintenance requirements from increasing their metabolic rate.
A cow needs to eat more roughage in cold weather to give her the calories for heat energy. If she doesn’t have enough roughage, she will rob body fat to create energy for warmth and loose body condition. More total pounds of roughage in her diet (extra grass hay, or even straw) can keep her warm, since the fermentation and breakdown of cellulose creates heat energy.
   Keep in mind that thin cows suffer more from cold stress and rob body fat stores to keep warm. Calves born to these thin, stressed cows may be weak and these cows may not produce adequate colostrum thus reducing calf survivability. In addition, the cow’s ability of these thin cows to breed back on time may be reduced.
Other important factors to consider are wet hair coats, wind, and mud. If a cow has good winter hair, she does fine until temperatures drop below 20° to 30° F. Below that, she compensates for heat loss by increasing her metabolic rate. Healthy cows, in average body condition and acclimated to cold weather have a “lower critical temperature point” (point at which maintenance requirements increase and you need to feed them more) of about 20° F.
   Lower critical temperature is defined as the lower limit of the “comfort zone” (below which the animal must increase its rate of heat production; it’s also the temperature at which performance begins to decline as temperatures become colder). Research at Kansas State showed that the critical temperature for a cow with a summer coat or wet coat is 60° F. It is 45° F for cows with a fall coat, 32° F for those with a winter coat, and 19° F for those with a heavy winter coat.
   Wind or moisture makes the effective temperature (the temperature felt by the body) lower than the temperature on the thermometer. Wind chill must be included when calculating the amount of degrees below a cow’s critical temperature point. For example, a 10 mile per hour wind at 20° F has the same effect as a temperature of 9° F with no wind. If the temperature drops to 0° F (or equivalent of zero, with wind chill) energy requirement of a cow increases between 20 to 30 percent – about one percent for each degree of coldness below her critical temperature.
  However, cattle can’t eat enough extra feed to compensate for heat production loss at -50° F with wind chill; they need windbreaks under these conditions to reduce heat loss during winter storms. During severely cold weather, cattle also need bedding to insulate them from the frozen ground, which will help conserve their body heat.
  Numerous factors will influence voluntary forage intake, cows may consume as little as 2.5 percent of their body weight as hay during mild conditions but may need up to 3.5 percent during severe cold. An important rule of thumb: increase the amount of feed (energy source) by one percent for each two degrees F of cold stress. For thin cows with poor hair coats, or in wet conditions (wet hair coat) figure a 1 percent increase for each degree of temperature drop. A wet storm is worse than dry cold. Wet hair loses insulating quality; the cow will chill sooner. When hair coat is wet, the critical temperature is about 59° F.
    When dry, the hair is fluffy and traps body heat in tiny air spaces between the hairs, creating a blanket of insulation between the cow’s body and the cold air. Hair tends to shed water fairly well for awhile, but once it gets completely wet and lies flatter, its insulating quality is lost and the cow is more easily chilled. A cow can suffer more cold stress in wet weather than in dry cold.
  Mud can also reduce the insulating ability of the hair coat. The relationship between mud and its effect on energy requirements is not as well defined, but depending upon the depth of the mud and how much matting of the hair coat it causes, energy requirements could increase 7-30 percent over dry conditions. In addition, there is research that suggesting mud may also be associated with decreased feed intake.
    Cattle need protection from the wind, especially during periods of bitterly cold temperatures and severe wind chill – exactly what we have been experiencing. Wind speed produces wind chill, which can further increase energy requirements for livestock. Cows who have lost weight or who are losing weight are very susceptible to cold or wet weather stress.
    Keep track of body condition as you winter your cows and provide them with highly digestible feeds that will provide their energy needs during the cold, snow, mud, wind, etc. ∆
DR. TERESA L. STECKLER: Extension Specialist, Animal Systems/Beef, University of Illinois

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