Cows in the cold: Preserving herds through extended cold periods
March 18, 2016
Maintaining beef cows in an average body condition score can help them persevere through extended periods of cold weather, according to a University of Nebraska beef extension specialist.
It's been a warmer-than-usual spring to date, but that doesn't mean a cold snap isn't around the corner. There are ways ranchers can be prepared and help get their cows through the cold if that does happen. Rick Rasby said the body condition score of 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 said. "Trying to adjust feed for cows when it is cold can be difficult. We may have a snap of cold weather for three or four days, or even a week. How do you 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 shared two charts during a recent presentation. The lower critical temperature (LCT) for cattle is based on haircoat, coat condition and body condition score. Basically, the chart says if the coat is more than one inch long, the coat is dry and the cow is in body condition score 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.
“If the cows are in average or better body condition, they can withstand cold temperatures easier than thin cows.”
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Producers also need to consider the Wind Chill Index (WCI), which shows producers when additional energy may be needed based on air temperature and wind speed. Cold stress is equal to LCT minus WCI, Rasby explained.
"Basically, the energy adjustment is one percent for each degree of magnitude of cold stress," he said.
In an example, Rasby explained 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 1 degree. So, the cold stress would be 19 – (-1) = 20. Adjusting the energy one percent for each degree of magnitude of cold would be 20 percent.
"If the TDN (total digestible nutrients) 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," he explained. "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 said. "There may be times you can't feed enough corn to give them the energy they need to withstand the cold. In really extreme cold conditions, the 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. 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 body condition score 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 said.
Cows can also be protected from the elements by having access to shelter. If producers have tree shelter belts or man-made shelter, like bales, canvas or tin, the additional energy needs of the cow will be reduced when cold weather hits because she is protected from the wind.
"Tree windbreaks or shelter belts work really well," Rasby said. "But, make sure they are designed so the cattle don't bunch up in cold weather. Also, if you are using it during calving, make sure there is enough room for all the cows so they don't trample the calves."
Bulls also need attention during cold weather.
"In extreme situations, the bulls can lose weight and body condition, and even have testicle damage or frost bite if they don't have adequate protection," Rasby said. "I would consider bedding for the bulls when it is cold, damp or muddy outside. I would also increase the energy in the diet for the bulls if it is cold for a long period of time." ❖