Dairy Calves Need Good Care and Management During Winter.

 By Heather Smith Thomas.

 Winter in some regions is not severe and management of dairy calves may not need to be much different than in other seasons.  In many areas of the U.S. however, winter is colder, wetter and more stressful for calves, so they need a bit of extra care.

At Birth
Dr. Whitney Knauer (Assistant Professor of Dairy Production Medicine, Department of Veterinary Population Medicine, University of Minnesota) says it is important to consider two critical periods for a young calf: the first 24 hours of life and the first four weeks.  At birth, the important thing (after making sure the calf is healthy and breathing) is to get that calf dry as soon as possible.  Calves lose body heat quickly when they are wet.  When calves don’t get dry fast enough, they become chilled and may not want to nurse, and they also may suffer frostbite.  “If we see frostbitten ears in pre-weaned calves, usually that’s a sign of not getting those calves dried soon enough after birth,” she says.

Air is a wonderful insulator, so we want the calf’s hair to be dry and fluffy, with tiny air spaces between the hairs.  If the calf’s hair coat is dry and fluffy, there is not as much heat loss from the body, compared with wet hair that is lying down flat on wet skin.

“If allowed, the cow can do a great job of licking the calf and removing birth fluids but then the best practice is to get the calf into a warm place.  One way to do this is with a warming room or warming box.  This gives the newborn calf a chance to adjust.”  It won’t be as much of a shock as going from the warm uterus to a cold environment.

Getting colostrum into those calves quickly is also crucial.  Besides all the IgG components that give the calf immediate protection from disease, colostrum contains a much higher fat content than regular milk.  This can help provide fuel for the calf to generate body heat.

“A newborn calf may only have a couple hours’ worth of energy reserve, so we want to get colostrum into the calf as soon as possible.  The colostrum needs to be fed at calf body temperature (about 102 degrees F) so she doesn’t have to expend energy to warm the colostrum in the abomasum,” says Knauer.  

Calf Jackets
Once the calf is dry, another option to help calves maintain body heat in winter is the use of calf jackets.  “Calf jackets should be placed on calves within the first day of life, after the calf is dried and before moving to a hutch or barn environment.  A good rule of thumb is that when the night and day temperatures together equal 90 degrees or less (such as 35 degrees at night and 55 degrees in the daytime, or colder) then a calf that’s only 3 weeks old or younger should wear a calf jacket,” says Knauer.

There isn’t much data to show that calf jackets improve health or performance, but she tells of one recently published study that indicated a difference.  “In that study, skin surface temperature was higher in calves wearing jackets.  In addition, in the week following jacket removal, calves previously wearing a jacket had a slump in feed conversion efficiency and average daily gain, indicating that the jackets were helping those calves maintain body temperature.  These results indicate that jackets can help calves maintain body temperature, potentially improving calf welfare,” she says.

Calf jackets can be removed when a calf is able to better maintain her body temperature, or at about 4 weeks of age.  “A calf experiences cold stress when the ambient temperature falls below her thermal neutral zone--below the temperature at which she has to expend energy to keep herself warm.  We consider that critical temperature to be about 60 degrees F in a young calf. When calves get to about a month of age, that critical temperature changes to about 32 degrees F (freezing).  This can also depend on calf housing strategy (barn versus hutch),” she explains.  

Dr. Arlyn “Jud” Heinrichs, Professor Emeritus of Dairy Science at Pennsylvania State University, says that the thermal-neutral zone for a young calf is between 50 to 77 degrees.  “When temperatures drop below 50 degrees, the nutrient needs for that calf will increase, to have enough energy for body maintenance and body heat.  The increase in these requirements start off slowly, but increase dramatically if the weather gets really cold,” he says.

“If you use calf jackets, you need to leave them on until the calves are weaned and start eating a lot of feed and are producing much of their own body heat via fermentation in the rumen,” he says.  If you start out with jackets on baby calves, you wouldn’t want to take those off partway through the suckling period because those calves may become dependent on the jackets and are not yet eating enough solid food to provide the necessary energy if you suddenly take the jackets off and the weather is still cold.

Feed
The newborn calf that is only getting milk or milk replacer needs extra energy, to meet the additional requirements in cold weather.  “Some people just feed more quantity while others add more fat, to provide the necessary energy.  There are many charts available on the web to show what the increased requirements would be, to counter the effects of cold stress,” says Heinrichs.

Knauer says that for every degree F that a calf is below her thermal-neutral zone, she needs 1% more energy just for maintenance requirements (not growth).  “For example when temperatures go from 60 degrees F down to freezing, a calf needs 30% more energy and we need to feed her more. We can accomplish this by changing the composition of the milk replacer (adding more fat and energy, for example) or by simply feeding the calf more milk or milk replacer,” says Knauer.

“We typically recommend adding a third feeding.  For example, if you’re feeding three quarts twice a day, we would recommend feeding three quarts three times per day.  Sometimes it’s a challenge from a labor perspective to add that third feeding, but we know that it’s really important for calf health and performance during the winter months. This is because energy is not only important for growth but also for immune function—to enable these calves to fight off scours and pneumonia pathogens.  They really need the extra energy during this time,” she explains.

Producers also need to offer water during the winter months, as well as a palatable starter, which can contribute to the energy needs of the calf.  “No one likes to deal with frozen water buckets, so we recommend offering warm water right after the calves have their milk or milk replacer.  You can leave the water there for an hour or so and then come through and dump it before it freezes.  Calves will learn this routine and know that this is when they can drink water,” she says.  

“To supply the necessary nutrition during cold weather, feeding more (a third feeding) or feeding something that’s a higher quality (bumping up the energy and fat percentages) will support maintenance, growth and immune function.  This should be done with the guidance of your veterinarian or your nutritionist, says Knauer.

After the calves’ rumens start to function and/or they are eating calf starter, somewhere in the range of 2 to 3 weeks of age, they will eat more solid feed to help provide that additional energy.  “They will get more energy in that feed, plus the fact that it’s fermenting in the rumen, and the fermentation creates heat also, to help keep the calf warm,” says Heinrichs.

The calf that’s 2 or 3 weeks old or older will be in a pretty good situation to handle cold weather, because the cold will stimulate appetite.  These calves will just continue to eat more solid feed.  This works well, as long as they are eating the starter, etc. and are not just on milk or milk replacer.

“Calves should always be encouraged to start eating starter when they are very young, any time of year, but this is especially important in cold weather,” he says.  A beef calf with its mother will mimic mom and start eating forage at a very early age, which stimulates rumen development.  Beef calves with their mothers will start chewing the cud by two or three weeks of age, but dairy calves have no role model and you need to help them figure it out.

Dairy calves will start chewing their cud too, as long as they have some fiber and particle size in their grain.  Even whole corn grain or oats will allow them to chew their cud.  “Sometimes people overfeed milk, and the calf is never very hungry and doesn’t start eating grain or starter right away.  It may be 6 weeks before they really start eating solid feed, and are relying on extra milk—which doesn’t do them as much good for physiological development,” says Heinrichs. The goal is to get a little more energy into the newborn calf, in cold weather, and start on solid feed as soon as possible.

Once the calves are eating grain and/or some forage, when the weather gets cold, their appetite increases.  “Between the rumen fermentation and the extra intake, those calves can do all right.  But the companies selling milk replacer may recommend just feeding additional quantities of milk replacer!  The first couple weeks of life, the additional milk or milk replacer really does make a difference because calves at that age do rely on milk for all their energy needs.  This is the time period in which you do need to make sure they are getting extra.  Encouraging grain intake as soon as possible is also important,” says Heinrichs.

Shelter
The other thing that is important for young calves in winter is adequate housing.  The environment of the calf and where she lives during those first few weeks of life can make a difference.  “Hutches do a great job of keeping calves warm as the calf’s own body heat can help maintain hutch temperatures in a comfortable zone, though Jersey calves have a harder time as they are smaller,” says Knauer.

The smaller calves also have more surface area (and more heat loss) for their volume compared to a Holstein.  In cold weather, a small newborn calf like a Jersey might chill more quickly than a large Holstein calf, and will have a higher energy requirement.  The larger calf can retain body heat a little better. Supplemental heat can be provided in a barn setting.

“It’s also very important to avoid drafts while maintaining proper ventilation.  This is often a fine line, but closing up a barn is not beneficial.  We need fresh air for those calves,” says Knauer.  Otherwise the air quality is poor, with dust and ammonia, which can irritate the lungs.  Fresh air is better.

“If they are in a nice hutch that has no drafts and is dry, with good bedding, the calves will nestle down into the bedding and they can stay warm—even if it’s zero degrees outside,” says Heinrichs.  This gives them a lot of protection.  A dry calf, that has adequate nutrition, can handle cold weather.  The dry hair coat provides insulation—holding in body heat, rather than letting it dissipate.  

By contrast, if a calf is wet, the hair loses its insulating quality and the skin also gets wet, and the calf will chill much quicker.  “Calves can essentially starve to death in the winter when they are wet.  If they don’t have good bedding or a dry area, or have to lie in a drafty place, they can’t stay warm,” he says.

Those calves become hypothermic and can literally “freeze to death” because they can’t retain enough body heat and are not getting enough nutrients to provide necessary energy.  “Even in moderate weather, calves that are wet don’t grow as well; it takes more energy to maintain body temperature.  There’s not enough additional energy for growth.”  They chill quicker, and burn too much energy (shivering, etc.) trying to stay warm.

“I tell farmers that a wet calf is like when a person steps out of the shower on a cold morning!  Those calves need to be dry,” says Heinrichs.  

Being dry and out of the wind, with good bedding, makes a big difference.  “We always recommend having enough bedding, such as a deep straw bed, so the calf can nestle down into it and is not just lying on top of it,” says Heinrichs.  Calves instinctively make a little nest so they can snuggle down into it, to stay warmer.  And if they’ve gotten up, when they decide to lie back down, they seek out that same warm spot (still retaining some warmth from their body), and lie in that same little spot.

“Calves spend the majority of their time (80% or more) each day lying down so we need to provide a comfortable, dry, warm place for her to lie,” says Knauer.  Bedding that insulates the calf, such as straw, is preferred in the winter.  Ideally, we want the bedding to be deep—at least 4 to 6 inches—so the calf can nestle down into it,” she says.

“We can actually score how the calf is interacting with bedding with a nesting score, which evaluates the calf’s ability to hunker down into the bedding.  We want to see all calves with a score of at least 2, and preferably 3 (legs totally covered with straw bedding) in the winter, as this helps insulate and also reduces air movement around the calf, helping her maintain her body temperature.”

One test a person can do in the barn is to kneel in the straw or bedding that the calf has access to.  “If your knees warm up, you know the bedding is adequate.  If your knees stay the same, that’s probably still OK, but if your knees get cold, that is a sign that the bedding is not sufficient for keeping the calves warm,” says Knauer.  In addition, if your knees are wet when you stand up, that is also a problem.  A wet calf is a cold calf.

“Most dairy people do a good job of providing shelter and adequate bedding,” says Heinrichs.  “If anything they overdo the milk/milk replacer feedings, but that’s not a bad thing.  As soon as the weather gets a little warmer they can back off on the extra milk and let the rumen get going with additional solid feed,” he says.

“Here in Pennsylvania, many folks get worried about cold weather and cold stress but we don’t have the extreme cold that many regions get.  Humidity makes a difference, however.  A dry cold is not as hard on animals as a damp cold, but our cold stress is not as severe as some of the more northern regions.”

Older Calves
Weaned calves can do well as long as they have reasonably good feed, if they have a good environment and can be dry and out of the wind.  “Rate of gain is poor on calves that don’t have a good environment.  Even in older calves it is important to have enough bedding in cold weather, and keep it clean.  Bedding can be changed, but in cold weather a lot of dairymen simply add to it, and the urine drains down through it and the top layers are dry,” says Heinrichs.

“After calves reach 4 weeks of age, they are typically over the most critical period as it relates to cold weather challenges,” says Knauer.  “At this point, we want to make sure they are getting enough energy through their milk and starter.  By the time they are weaned, they can more easily tolerate colder temperatures with fewer negative consequences.”  At and after weaning, make sure their ration is balanced to maintain and promote growth and health, and that their environment is ventilated but not drafty, and that they have enough bedding to maintain warmth.   

Heat Stress
With young calves, heat stress is actually worse, and harder on them, than cold stress.  “People tend to ignore or forget about that.  What happens with heat stress is that the calves lose their appetite in hot weather and eat less.  They can also dehydrate readily,” says Heinrichs.

“They need more water in hot weather—and not just milk or milk replacer.  They are also burning calories because the body has to work at staying cool, and if they are also eating less they tend to grow slower.”  Thus with any extremes in weather, whether cold or heat, calves need more care and management to ensure good health and optimum growth.