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While trying to maintain its body temperature in cold weather, an 88-pound newborn calf can run out of energy in just 18 hours. That’s why it’s so important to provide sufficient energy to young calves in the winter.

However, research suggests that only 33 percent of dairy producers change calf feeding practices when temperatures drop. Use the following information to gain a better understanding of calf energy requirements and how to supply energy for body maintenance and growth this winter.

1. Meet daily energy requirements

According to Jim Drackley, nutritionist at the University of Illinois and co-author of the book, “The development, nutrition and management of the young calf,” a young calf needs approximately 17.5 kilocalories to 20 kilocalories of energy for every pound it weighs to maintain body functions under normal conditions in the “thermal-neutral zone,” which ranges from 50 F to 78 F. But, when temperatures drop below 50 F, the calf must use extra energy to maintain its body temperature.

To estimate energy needs, you need to get a handle on how much your calves typically weigh at birth. “While most Holstein calves weigh around 75 to 95 pounds at birth, the weights vary from farm to farm due to genetics and dry-cow nutrition,” says Troy Scott, technical service manager with Milk Specialities. By weighing or taping a portion of newborn calves on the farm, you can estimate the energy needs of young calves.

In addition to maintaining a calf’s body weight, you also want to support growth with the milk or milk replacer you feed. In the table, “Maintenance and growth energy requirements in the thermo-neutral zone,” at right, average maintenance requirements for young calves and the amount of energy to obtain growth rates are shown, based on specific energy equations calculated by Drackley.

For example, the table shows that a 80-pound calf needs 1,478 kilocalories for maintenance, and an additional 853 kilocalories to achieve 0.5 pounds of growth per day, or 2,331 kilocalories of energy per day.

2. Know how much energy you’re supplying

The general rule of thumb in calf feeding is that 1 pound of 20 percent protein and 20 percent fat milk replacer per day provides around 2,000 kilocalories of energy, says Rob Costello, technical specialist with Merrick’s, Inc.

To be more specific, you can use a few additional calculations and the information provided on the tag of your milk replacer to calculate the energy level.

First, you need to know the number of grams fed per calf per day (1 pound equals 454 grams), the percent protein, percent fat and percent carbohydrates in the milk replacer. Many tags do not list the percent carbohydrates. However, Scott says you can estimate this amount by subtracting the protein percent, fat percent and ash percent from 100. If the percent ash is not listed, use an estimate of 10 percent.

The equations you plug these values into are shown in an example for feeding 1 pound of a 20 percent protein, 20 percent fat and 50 percent carbohydrate milk replacer:

454 grams x 0.2 protein x 4 = 363 kilocalories

454 grams x 0.2 fat x 9 = 817 kilocalories

454 x 0.5 carbohydrates x 4 = 908 kilocalories

Total kcals: 363 + 817+ 908 = 2,088 kilocalories

For those of you feeding 4 quarts of whole milk to calves per day, Drackley estimates that typical Holstein milk supplies 2,600 kilocalories, while Jersey milk typically supplies 3,000 kilocalories. “Most producers assume that milk replacer has the same energy values as whole milk, but it doesn’t,” says Costello.

It also might surprise some producers that 1 pound per day of the typical 20 percent protein/20 percent fat milk replacer supplies only enough energy for a 90-pound calf to maintain its body and gain one-third of a pound per day.

Some producers feel that feeding just enough energy is OK until they can get calves consuming starter feed. That’s because 1 pound of starter provides 1,300 to 1,500 kilocalories. However, experts say liquid feed should be the principle source of nutrients for the first two weeks of life, or until the calf consumes 1 pound of starter.

“We’re encouraging producers to not just keep the calf alive in the first few weeks of life, but really focus on getting calves to grow and develop in that time period,” says Scott.

3. Adjust for cold stress

While 50 F seems like a pleasant fall day, young calves start burning calories to maintain body heat at this temperature. The farther temperatures drop, the more energy the calf needs to maintain itself. A common guideline: for every degree Fahrenheit the temperature drops below 50, energy intake increases by 1 percent. For example, if an 80-pound calf requires 1,478 kilocalories at 50 F, it would require an additional 443 kilocalories at 20 F (1,478 x 0.3 = 443).

However, you can easily boost energy levels in the milk you supply. Options include:

  • Feed a milk replacer with more energy. Costello says many producers in the Northwest and Michigan like to feed a 20 percent protein/24 percent fat milk replacer to all calves throughout the entire winter. By adding more fat — in this case around 164 kcals of energy per day — to the milk replacer, calves get a little extra energy with the same number of feedings and the same mixing and preparation procedures.

    And, adding fat to product is a pretty cheap source of energy — the 20/24 milk replacers cost around 87 cents to 90 cents per pound, or approximately 3 cents to 5 cents more than 20/20 milk replacers.

    However, unless fed according to label recommendations, the 30/15 milk replacers that you’ve heard about for accelerated growth should not be used to boost energy levels for short durations during cold stress. These programs are developed for growth rates between 1.5 and 3 pounds per day and require completely different feeding regimes than 20/20 milk replacers, says Scott. And, the high protein level in 30/15 products boosts the price to around $1 per pound.

  • Add a fat supplement product into your milk or milk replacer. Fat supplements added to mixed milk replacer also boost the energy content. This type of product, fed at about 4 ounces per day in addition to milk replacer, adds about 752 kcals to the calf’s diet — at a cost of around 20 cents per calf per day. Or, a total liquid feed cost of $1.04 per calf per day.
  • Increase the amount of milk replacer fed. Increasing the volume of milk fed at each feeding, or feeding calves three times a day, also can increase the energy supply. For example, if label instructions call for feeding 1 pound of milk replacer per calf per day, you would feed 1.25 pounds during cold stress. For most 20/20 milk replacers, this provides an additional 522 kilocalories of energy. With 1 pound of milk replacer costing around 84 cents, feeding 1.25 pounds would cost $1.05 per calf per day.

    When supplying additional milk replacer, be sure to increase the volume fed instead of feeding a more concentrated product. For example, if mixing 1.25 pounds of milk replacer per day, feed 5 quarts of milk per day or 2.5 bottles, not a more concentrated 4 quarts, or two bottles. “Calves are creatures of consistency,” says Sheila McGuirk, veterinarian at the University of Wisconsin. Make sure that their milk replacer tastes and digests the same way every day.

    Some producers simply feed calves three times a day during cold weather, supplying 1.5 pounds of milk replacer per day. While this increases the feeding frequency, it does not change the mixing or preparation procedures. An extra 2 quarts per day would supply an additional 1,044 kcals, with total liquid feed costing $1.26 per calf per day.

    Although cold temperatures can make feeding water difficult, be sure to supply ample amounts to calves at some point during the day when increasing the energy levels. In some cases, this might increase the amount of sodium fed, which increases the calf’s water requirements.