Manage winter stress on animals
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Factors that create stress during the winter months are cold, wind, snow, rain and mud. The primary effect on animals is due to temperature. All these factors alter the maintenance energy requirements of livestock.
Maintenance requirement can be defined, as the nutrients required for keeping an animal in a state of balance so that body substance is neither gained nor lost. An interesting thing to note is that while energy requirements increase, protein requirements remain the same.
Some published sources contain nutrient requirements for beef cattle that include guidelines for adjusting rations during winter weather. Even without published sources, competent livestock producers realize the need for more feed during cold weather.
Make sure that water is available. If water is not supplied, cattle will reduce feed intake.
There is a range of temperatures where cattle are neither too hot nor too cold and their performance is optimal. This temperature range is called the thermoneutral zone. It is the temperature range where fewest nutrients are needed to maintain bodily functions. For cattle the lower temperatures are: 60 degrees in the summer or when hair coat is wet; 45 degrees with a dry hair coat in the Fall; 32 degrees with a dry hair coat in the winter; and 19 degrees with a dry heavy winter coat. All of the critical temperatures listed are effective ambient temperatures, which basically means the wind chill temperature is used if the cattle are not sheltered. The critical temperatures also take into consideration the insulating ability of the cattle, as shown by the change between a wet and dry coat.
If we have a choice, snow is preferred to a cold rain. We lose what is called “air insulation” in cattle that get wet versus those that are out in the snow. The air pockets between hair fibers are a source of insulation. We lose this insulation when hair gets matted down in a cold rain. The result is that the dry winter coat goes from having a critical temperature of 32 degrees to about 59-60 degrees.
From several studies it is estimated that for every 1 degree below the critical temperature, a cow’s energy requirement increases 1 percent. It is also estimated that for every 10 degrees below the critical temperature, the digestibility of the ration decreases by one percent. This means that when the temperature drops below the critical temperature, the cattle need to be fed better. It may be that more or better hay needs to be fed.
Besides cold weather effecting cattle performance, producers have another thing to consider during winter, mud. It is less clear what effect mud has on a cow’s energy requirements but it is estimated that it can increase the maintenance requirement from 7 to 30 percent. If cattle have to deal with mud, then their ration should also be improved.
