Farming Magazine - January, 2010


Dairy Nutrition: Cows Get Cold, Too

By John S. Hibma

I think I’ve got it figured out now that I’ve lived in New England for 10 years. The coldest month of the year tends to be January. Prior to moving to New England I had always thought that the existence of snowbirds was merely a myth. Dairy farmers, as best as I can tell, stoically tolerate the winter weather. Most of them, I’m pretty sure, though, hate winter with a passion. Some of them, I believe, will eventually morph into snowbirds.

Dairy cows, as it turns out, tolerate the colder weather much better than they tolerate hot and humid weather. A great deal of research has been conducted on heat stress in dairy cows with much having been written about it. It’s much more challenging to keep a herd of cows cooled down in hot conditions than it is to keep cows warm in extreme cold. Since cows are heat-generating machines, keeping cows warm during the winter is more about having adequate housing and using common sense. 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.

Dairy cows are happiest when the ambient temperature is just above freezing to about 50 degrees and humidity is very low. I do believe that cows have smiles on their faces when they can see their breath. This, of course, is problematic for Homo sapiens, who can’t stand the temperature below 50 degrees. Even though many dairies are located in locales where winter temperatures dip below 0 degrees, 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.

However, we all know that when the winter storms come roaring from out of the north and everything outdoors freezes solid, energy must be available and used to keep things warm and functioning. Cows are warm-blooded and need to maintain a core temperature of about 101 degrees. Just as in humans, hypothermia will eventually affect a cow if temperatures remain below freezing long enough.

Cows naturally try to compensate for colder temperatures by increasing feed intakes. Given the opportunity, cows will eat more when it’s cold. Grains and commodity by-products 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 they metabolize that fat, it will become that much more difficult to keep warm and eventually hypothermia will set in. In addition, as more calories are used for a milk cow’s body maintenance, less energy is available for milk production. In the extreme condition, skinny cows that have been underfed during the winter are hardly in a position to make milk.

In the U.S., we measure energy in calories and in 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. The opposite is true, as well. Cows are the same way. Massive amounts of calories are needed to meet a cows 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.

So, what do we need to do to feed cows properly in extremely cold weather? First and foremost we expect those cows to eat more to get the necessary energy to compensate for the colder temperatures. A typical feed ration that’s 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. Later on in January, when the daytime temperature doesn’t climb above 20 and nights are well below freezing, that same cow must eat another 4 pounds of dry matter to compensate for her increased energy needs.

The most efficient way to get those extra calories into your cows is with feedstuffs that are calorie-dense. Sure-fire products that will deliver calories to cold cows are the rumen-protected fats that are available from your feed suppliers. However, those products are not inexpensive and with the current economic crisis in the dairy business, you need to look carefully at all the alternatives. Neither should you 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 over-feed those expensive ingredients.

Reformulating your dairy cow diets is usually the most cost-effective means of getting increased feed levels into your cows during the winter without breaking the bank. In this current economic climate, every dairy farmer should be formulating his or her cows’ and heifers’ diets with the aid of computerized ration evaluators that incorporate least-costing routines. Nutrition modeling software such as CPM and CNCPS do an amazingly accurate job of formulating rations that meet nutritional needs for a wide range of temperature and humidity combinations.

By the time you read this, it will most likely be a cold winter’s day in New England and your cows could already be on the downward slope of losing body conditions that will eventually impact their health, reproduction and milk production come spring time. There’s a lot of uncertainty in the future of our industry as we turn the calendar over and begin 2010. Keeping your cows healthy and productive throughout the winter will put your dairy business in a good position when the milk prices finally start to turn around.

The author is a dairy nutritional consultant and works for Central Connecticut Farmer’s Cooperative in Manchester, Conn. Comment or question? Visit and join in the discussions.