Preventing Cold Stress in Cattle

Importance of Adequate Herd Nutrition

Preventing Cold Stress in Cattle

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Cold stress in cattle adversely affects cattle health and well-being. Stressed animals are more vulnerable to illness. Cattle generally need more care during cold or wet weather and this includes additional feed. Providing adequate nutrition to cows and calves can reduce incidence of illness or loss of animals.

Cattle that have a chance to acclimate gradually to winter develop a thick hair coat and put on body fat if feed sources are adequate, enabling them to withstand much colder temperatures, but some situations put them at risk for hypothermia. Conditions that lead to cold stress in cattle include wind, in combination with cold temperatures, wet weather (which negates the insulating quality of a fluffy hair coat), and inadequate forage.

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Hungry cows are cold cows; forage is broken down and digested in the rumen by microbial action, and this fermentation/breakdown process produces heat. Cattle eat more in cold weather to generate adequate body heat.

With short summer hair, cows may chill (and need more food) when temperatures drop below 40 degrees F, whereas cattle with a heavy winter coat can stay comfortable at temperatures below zero if there’s no wind. They also adjust to cold weather by increasing metabolic rate. Increased metabolism increases heat production and will also increase appetite and they eat more.

Feed intake increases and passage of feed through the digestive tract speeds up. Feed requirements for cattle in cold weather may go up 10 to 15%. All of these changes contribute to an increase in heat production so the animal can withstand winter temperatures. If a cow gets too cold, however, heat loss and cold stress reduce appetite and decrease her efficiency of feed conversion. Body metabolism is adversely affected if body temperature drops. Mammals must maintain a fairly constant body temperature to keep up the metabolic processes that enable the body to function.

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If temperatures drop below the animal’s comfort zone, there’s not only an increase in maintenance requirements, but digestibility is reduced. This further increases the feed needs of cattle. Research has shown there’s a decline of about 1% in feed digestibility for every two degrees of temperature drop, but cattle that are adapted to cold weather have more efficient digestion at cold temperatures and are more resistant to the depressing effects of cold on digestion.

Body condition is extremely important. Cattle that get too thin during a cold or wet winter suffer more cold stress than fatter cows (since fat serves as insulation and a source of energy reserves). A thin cow must rob even more body fat to burn as energy to keep warm. It becomes a vicious cycle.

If a cow has a good winter coat, she does fine until temperature drops below about 20 degrees F. Below that, she must compensate for heat loss by increasing energy intake, to increase heat production and maintain body temperature. Healthy cows in average body condition (body score 5 on scale of 1 to 9) or higher, acclimated to cold weather, have a lower critical temperature point. This is the point at which maintenance requirements increase and you must feed them more. This is the lower limit of the comfort zone, below which the animal must increase the rate of heat production.

Lower critical temperature for cattle depends on hair coat and how much fat layer is under the skin; a heavy winter coat provides much more insulation than summer hair and they won’t need extra energy to keep warm until temperature drops below that point or they get wet. If cows are not receiving extra nutrition to provide the needed body heat, they burn fat and lose weight. Weight loss during late gestation will result in lower pregnancy rates the next breeding season.

In cold weather, cattle need more roughage in the diet, either as pasture or grass hay or good quality straw. Then they can keep warm — as long as they have enough protein to feed the rumen microbes that ferment and digest roughage. A little alfalfa hay or a protein supplement should be added to the diet if cattle are grazing mature, dormant pastures in winter, or being fed grass hay that’s low in protein. The additional protein will enable them to utilize more forage. Well-fed cattle that can get out of the wind, with shelter from wet weather, won’t suffer hypothermia symptoms.

If weather is cold and windy, cows must eat more. If they spend all their time behind windbreaks or huddled in a group to protect themselves from wind, rather than grazing, they can’t eat enough to maintain body heat. Even if pasture is available, they may not start grazing until temperatures are warmest in midday, and lose weight because they’re not eating enough. Under these conditions you need to feed hay or a supplement early in the day to get them going, and then they’ll usually start grazing.

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What to Feed

In cold weather, high-quality leafy alfalfa by itself is not the best feed. Even though it supplies plenty of protein, calcium, vitamin A, and other important nutrients, it doesn’t have enough fiber to provide heat energy during cold weather. Cattle fed high-quality hay as their only forage source may lose weight. Alfalfa alone is not adequate for cattle when weather is really cold; they gobble it up and stand around shivering. They need more fiber in the rumen to create heat energy.

If cows are cold, they need all the roughage they’ll clean up. You can’t feed that much high-quality alfalfa or they may bloat. Beef cattle don’t need dairy quality alfalfa and it isn’t the best feed for cold weather. Alfalfa for beef cows can be lower quality (more stems/fiber and less leaves) or a grass/alfalfa mix if fed as the primary forage source, or fed in small quantities as a protein supplement. A small amount of good alfalfa per day (or the daily alfalfa ration doubled and fed every other day) can supply the “gut bugs” with adequate protein to do their job, and augment protein/mineral/vitamin levels of poor-quality roughage such as dry pasture or low-quality grass hay or straw. Alfalfa or protein supplement can balance the diet and enable cows to utilize poorer quality forage to best advantage. When it gets really cold, cows do fine if you feed as much poor-quality roughage they can eat — straw or low-quality, mature grass hay — and enough alfalfa or protein supplement to provide the necessary protein for digesting it.

Cold Stress in Calves

Nutrition of the pregnant cow makes a difference in the health and strength of her calf. Pregnant cows in cold weather need adequate feed for their own maintenance, warmth, and for the pregnancy, also for creating adequate good-quality colostrum. Calves born to thin cows may be compromised in body condition and immune health — more prone to disease during their first weeks of life. They may be born weak, unable to get up quickly and nurse — not getting colostrum soon enough. Cold stress also hinders a calf’s ability to absorb the antibodies in colostrum. Thin cows may not produce adequate levels of antibodies in their colostrum if their diet has been short on protein. Calf survivability is lower in thin cows, and the thin cow’s ability to rebreed is hindered.

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Newborn calves in cold weather are at much greater risk for cold stress than their mothers, even if they had adequate nutrients during gestation. They are wet, and chill quickly unless mama licks them dry. Her rough tongue pulls off birth fluids, fluffs up the hair, and enables a calf to dry faster. The calf must suckle as soon as possible, since colostrum not only provides important antibodies against disease but also contains nearly twice as much fat as regular milk, providing instant energy for keeping warm. Nutrients in colostrum enable the newborn calf to more readily withstand cold temperature. Once he’s nursed and dry, he won’t get as chilled.

Young calves don’t have a functional rumen and can’t produce as much body heat (via rumen digestion/fermentation of forage) as a cow. They also don’t have as much body fat for insulation. If a calf is born in cold weather, make sure he gets dry quickly and can get up and nurse. Also provide shelter for young calves so they can get away from wind. They don’t handle wind chill very well because of their small body mass.

Windbreaks and Bedding

Natural windbreaks of trees/brush make good protection and can prevent cold stress in cattle. In pens or pastures without natural windbreaks, boards on fences can reduce wind chill by up to 70%. In extremely cold weather, provide bedding (straw, wood chips/shavings) for cattle. Without bedding, energy requirements in sub-zero weather may increase by 12 to 15% on a cold night, and cattle must have more food, just to offset the heat lost when they have to lie on cold ground.

Now that you know the importance of preventing cold stress in cattle and supplying proper nutrition, what changes, if any, will you be making?

Originally published in Countryside January/February 2020 and regularly vetted for accuracy.

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