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Wind Chill Affects Cattle

Keep cattle dry and out of the wind to save on winter feed costs.

In northern climates where wind chill can be a big issue during colder months, planning ahead for winter weather can save money in reduced feed costs, reduced illness and health costs, less loss of body condition and better gains on young animals. If there are no natural windbreaks, artificial wind barriers can be created.

David Ames, retired environmental physiologist at Colorado State University, was originally at Kansas State University where he worked on cold-weather effects on cattle and developed wind chill indexes for cattle.

“Realizing the value of windbreaks came from understanding the wind chill factor. Impact of wind chill in combination with energy requirements for cattle during cold weather suggests there is value (in feed savings, well-being of the animals, etc.) if cattle are protected from wind when temperature drops below their thermoneutral zone (critical temperature),” he says.

Ames established the critical temperatures for cattle, along with wind chill index.
“The wind chill index for humans was developed by the army for smooth skins (no hair),” he explains. “It was developed using a plastic bag full of water in different wind speeds during cold to determine how fast the temperature in water would drop. The difference between humans and livestock is a hair coat.”

The hair stands up, with tiny air spaces creating excellent insulation to hold body heat in and keep cold out. This hair “blanket” works well to keep cows warm — unless the hair gets wet and flattens, allowing moisture next to the skin. When animals get wet, they are as vulnerable to cold as if they were smooth-skinned. The wet in combination with cold is more stressful than just wind and cold.

Cattle do well, in terms of energy costs, until wind breaks the hair barrier down, which it can do even if the animal is dry, if wind is strong enough.

“If it separates the hairs, the insulating quality is lost. It blows holes in that hair coat,” he explains.

“In those conditions, windbreaks become more important. Wind can separate the hairs at something more than 10 miles per hour. The first response of a cow is to try to get out of the wind,” he says. This is when cattle head for the trees/brush, into a draw or use a manmade windbreak.

“When animals get cold, it takes about 1% more feed for every degree (F) of cold,” he explains. “With a winter hair coat, cows don’t start to get cold at the same temperature as when they are wet. In summer hair or wet, they start to get cold at about 50° F. With dry winter hair, that critical temperature can be below 20° F. They may not be stressed at all at 10° on a winter day. If they have a full hair coat, cows may not need any protection, but wind chill can take that temperature down to an effective temperature of minus 10° and windbreaks have value.”

Some of the coldest days for cattle are when temperature may be higher but they are wet.

“A wet day with wind at 32° is more stressful than zero on a sunny winter day, and if they are standing in mud, this is a huge energy drain. If you can influence any of those factors — keep them dry and out of the wind — this improves their energy efficiency and lowers your feed costs during temperatures below their critical point,” says Ames.

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Editor’s Note: Heather Smith Thomas is a freelancer and cattlewoman from Salmon, Idaho.



 


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