It’s December and the cold weather is coming. Cold weather affects our dairy animals much more than we realize. Calves will not grow as fast as they should and fresh cows will have more metabolic problems that often persist through the lactation, lowering total milk production.

The challenges coming from cold weather are deceptive and start off slowly. October can remain warm and we’re in denial that winter is only a couple of months away. Autumn is fully upon us and yet fresh cows show no signs of metabolic disorders and calves seem to be growing just fine. Sometimes it snows in December and sometimes it doesn’t – but it’s certainly colder than it was in November. Then January shows up and suddenly our world plunges into a deep freeze.

Prepping animals for cold temps

Animals that are exposed to extremely cold temperatures must use more energy to stay warm – energy that in the warmer weather would be used for growth or milk production. Cows, heifers and calves that are exposed to long periods of extreme cold with no adjustments to their diets or environment will not be able to maintain body condition and, eventually, their health and milk production will be negatively affected.

Cows are warm-blooded mammals that must maintain a core temperature of about 101 degrees Fahrenheit. And just as in humans, hypothermia will eventually affect a cow if temperatures remain below freezing long enough and caloric intake is not increased. Cows naturally try to compensate for colder temperatures by increasing their feed intakes. Grains and commodity byproducts offer more energy per pound than forages. In fact, when temperatures become extremely cold, forages alone will not supply enough calories to keep cows warm.

If cows – as well as heifers and calves – are not fed enough to compensate for cold temperatures, they will begin using their body-fat reserves to meet energy requirements. As more calories are used for a milk cow’s body maintenance, less energy is available for milk production. In the most extreme conditions, skinny cows that have been underfed during the winter are hardly in a position to make milk the following year. Cows that freshen in extremely cold weather will spend more time in a negative energy balance and be much more prone to metabolic diseases such as ketosis and milk fever.

In the United States we measure energy in calories, and in dairy nutrition, we refer to energy as kilocalories (kcal) or megacalories (mcal). Calories are funny things. We all need them but when we consume too many relative to the work we do, we’ll get fat. And the opposite is true, as well. Cows are the same way. Massive amounts of calories are needed to meet a cow’s energy needs for both maintenance and to produce milk. Extremely cold weather requires more calories in the diet to generate more heat, keeping the metabolism functioning.

Photo courtesy: steverts/istock

Dairy cows’ weather preferences

Dairy cows, as it turns out, tolerate cooler weather much better than they tolerate hot and humid weather. They are happiest when the ambient temperature is just above freezing to about 50 degrees Fahrenheit and humidity is very low. Since cows are heat-generating machines, keeping cows from extreme cold during the winter is more about having adequate shelter or housing. For the most part, metabolic challenges resulting from extreme cold are seldom an issue so long as cows remain in a positive energy balance and are not losing significant body condition. And though many dairies are located in locales where winter temperatures dip below 0 degrees Fahrenheit, cows are kept inside barns that are buttoned up tight and temperatures can remain above freezing, aided by the cows’ own capacity to generate heat.

So what do we need to do to feed cows properly in extremely cold weather? First, those cows must eat more to get the necessary calories to compensate for the colder temperatures. Extra feed must be made available. A typical feed ration that has been balanced in the fall when daytime temperatures are in the mid-60s calls for a cow to consume about 45 pounds of dry matter to support 70 pounds of milk production. In January when the daytime temperature doesn’t climb above 20 degrees Fahrenheit and nights are well below freezing, that same cow must eat another 4 pounds of dry matter just to compensate for her increased energy needs.

Best type of feedstuffs

The most efficient way to get those extra calories into your cows is with feedstuffs that are calorie-dense. Reformulating your dairy cow diets in preparation for the winter is the most cost-effective means of increasing caloric density in the diet. A surefire product that will deliver extra calories to cold cows are with the rumen-protected fats that are available from your feed suppliers. Also, it’s not advised to just take a current feed mix and increase the amounts without re-evaluating. This may not be the best solution since vitamins and minerals are formulated to correct levels with a specific inclusion rate of a grain mix. Increasing will only overfeed those expensive ingredients.

When the ambient temperature (Fahrenheit) drops into the teens or less, the energy requirements for prenatal calves doubles. Calves are born with very little body fat and the only way they can get calories for both growth and maintenance is through their diet. When the weather turns nasty cold and the temperature in the calf hutches is below freezing for most of a day, solids intakes for prenatal calves must be increased. Even though the cold weather may only persist for a month, your calves, while not getting sick and dying, will not grow a speck unless both calories and protein levels are increased. The newer high-fat/high-protein milk replacers add significantly more nutrition to a prenatal diet.

The trick to managing through the cold months is to get a head start on it before the temperature drops. Having a plan in place for diet changes that increase caloric density will pay off in the long run. In fact, it would be prudent to implement a high caloric diet to both milk cows and calves as early as December 1 because sooner or later the animals will need it.

Cover photo: steverts/istock