Cows in average body condition able to withstand sustained winter storms
According to a University of Nebraska Extension beef specialist, maintaining beef cows in an average body condition score (BCS) can help them persevere through extended periods of cold weather, Rick Rasby tells producers the body condition score of their cows is like their insurance policy or risk management strategy.
“If the cows are in average or better body condition, they can withstand cold temperatures easier than thin cows,” he says.
“Trying to adjust feed for cows when it is cold can be difficult,” Rasby explains. “We may have a snap of cold weather for three or four days, or even a week. How do we change the ration for the cows so they get enough energy?”
To help producers determine the trigger point when cows need more energy because of cold weather, Rasby tells producers to refer to two numbers.
The lower critical temperature (LCT) for cattle is based on hair coat, coat condition and body condition score.
Basically, if the coat is more than one inch long, the coat is dry and the cow is in BCS four, she can withstand temperatures as low as 27 degrees Fahrenheit before she needs additional energy.
However, if her coat is wet or muddy, she will need additional energy when the air temperature falls below 61 degrees.
Producers also need to consider the Wind Chill Index (WCI), which shows when additional energy may be needed based on air temperature and wind speed. Cold stress is equal to LCT minus WCI, Rasby explains.
“Basically, the energy adjustment is one percent for each degree of magnitude of cold stress,” he says.
A little math
As an example, if the winter haircoat is dry and heavy, the LCT would be 19 degrees. If the air temperature is 10 degrees and the wind speed is 10 miles per hour, the WCI would be negative one. So, cold stress would be 19 minus negative one, which equals 20. Adjusting the energy one percent for each degree of magnitude of cold would be 20 percent.
“If the total digestible nutrient requirement is 12.2 pounds per head per day, then 12.2 pounds per head per day multiplied by 1.20 for a 20 percent increase in energy would be 14.6 pounds per head per day,” Rasby explains. “If hay is 56 percent TDN, then 14.6 pounds divided by 56 would be equivalent to 26.1 pounds of dry matter.”
Rasby also cautions producers that, if it gets cold enough, they may not be able to feed enough additional energy to maintain their cows if they are in too low of a body condition score.
“Body condition is important to help the cows through extended periods of cold,” he says. “There may be times we can’t feed enough corn to give them the energy they need to withstand the cold.”
“In really extreme cold conditions, cows won’t be worried about eating. They will be focused on trying to stay warm and get to shelter to stay out of the cold,” he adds. “If it is cold for an extended period of time, I would feed extra energy, so they don’t lose weight.”
If producers calve in March and have their cows in a BCS of five or better, they should be able to manage for inclement weather, even if the cold weather is prolonged over several days.
“They may just need to feed some additional energy,” he says.
Cows can also be protected from the elements by having access to shelter. If producers have tree shelterbelts or man-made shelter – like bales, canvas or tin, the additional energy needs of the cow will be reduced when cold weather hits because they are protected from the wind.
“Tree windbreaks or shelterbelts work really well,” Rasby explains. “But, make sure they are designed so the cattle don’t bunch up during cold weather.”
“Also, if producers are using shelterbelts or windbreaks during calving, make sure there is enough room for all the cows so they don’t trample the calves,” he adds.
Bulls also need attention during cold weather.
“In extreme situations, bulls can lose weight and body condition, and they may even have testicle damage or frost bite if they don’t have adequate protection,” Rasby emphasizes.
“I would consider bedding for the bulls when it is cold, damp or muddy outside,” he states. “I would also increase the energy in the diet for the bulls if it is cold for a long period of time.”
Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.