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Focus on energy sources for optimal calf performance

Tom Earleywine Published on 11 September 2015

091615-earleywineMost of a young calf’s nutrition is supplied via milk or milk replacer during the first two to three weeks of life, making it the young calf’s only source of energy. Starter grain fed during this time does not supply a significant amount of additional energy, as it is primarily fed for rumen development.

To maximize the value of a calf-raising program, producers should manage their calf nutrition program for 1.75 to 2.25 pounds of average daily gain per calf through the pre-weaning phase. The goal is to double a heifer’s birthweight by the time she reaches 56 days old.



Temperature makes a difference

Like all animals, calves have a “thermoneutral zone” in which their environment does not affect their nutritional needs. A number of environmental conditions contribute, including age of the calf, bedding, wind, precipitation, humidity and shelter.

But outdoor temperature is the main factor, and the thermoneutral range for calves is fairly narrow – approximately 60 to 75ºF. Under thermoneutral conditions, a 100-pound calf needs approximately 4.13 mega-calories of metabolizable energy (ME) per day to achieve a rate of gain of 1.76 pounds per day (Table 1).

calf nutrient requirementsWhen temperatures fall above or below that range, calves require additional energy to maintain core body temperature. If those requirements are not supplied via nutrition, they will be taken from the calf’s energy stores, resulting in weight loss, impaired immune function and possible illness or death. The volume of liquid nutrition needed to meet calves’ maintenance requirements and gain 1.5 pounds per day despite environmental conditions are shown in Table 2.

calf milk replacer needsDon’t let energy be a limiting factor to calf performance during times of stress; implement a feeding program that supports these increased energy demands.

A full potential diet provides optimal nutrition

The traditional method of feeding approximately 2 quarts of milk or 20:20 milk replacer twice a day falls far short of the energy and protein requirements to support both maintenance and growth of young calves (Table 3).


calf nutritional requirementsFeeding 4 quarts twice a day or 3 quarts three times a day of a full potential liquid diet with the correct balance between fat and protein can deliver the necessary nutrient levels. More frequent daily feedings, feeding higher volumes of milk replacer and automatic feeders are excellent ways to deliver full potential feeding.

Recognizing the importance of energy to calves is necessary to understand the most beneficial way to deliver it.

Fat is not the only source of energy in milk or milk replacers

Energy is predominantly derived from two sources – fat and carbohydrates. The predominant source of carbohydrates in milk or milk replacer is lactose. Milk replacer is generally comprised of about 35 to 45 percent lactose.

Carbohydrates are rapidly digested and provide nearly “instant energy.” Fat is stored for longer-term use and is a reserve energy source that is mobilized as needed.

Low fat does not equal low-energy

Keep in mind that just because a milk replacer product has a low fat percentage does not necessarily mean it is a low-energy product.

It’s about the proper protein-to-energy balance

The balance between fat and protein levels also plays a key role in optimal calf nutrition. Excessively high fat levels (above 20 percent) can suppress starter intake and result in heifers that have poorer feed efficiency and may not meet growth and breeding benchmarks in an economical time frame.


A good rule of thumb is to try to achieve at least a 2.5-to-1 ratio of protein to fat in the milk replacer diet of large-breed calves in warm weather and at least 1.4-to-1 in the winter when feeding a high plane of nutrition.

Fat is not a generic ingredient

The source of fat in milk replacer is an important and often-overlooked consideration. Milkfat, due to its high value in the human nutrition market, usually is not used in calf milk replacers. That leaves alternative sources to supply fat in milk replacers, which traditionally have been lard, choice white grease or tallow.

The fatty acids that make up fat are classified as short-chain, medium-chain and long-chain fatty acids. The length of the chain depends on the number of carbon atoms that make up the structure of each fatty acid.

Medium-chain fatty acids are highly digestible, as they are absorbed directly from the small intestine to the liver, where they are converted to available energy.

Certain polyunsaturated fatty acids (omega-3s) modulate the inflammatory response by the calf’s immune system, allowing the calf to recover more quickly from an immune challenge.

The key to optimizing fatty acids is to formulate their balance in milk replacer to mimic their levels in cows’ milk. While a good share of cows’ milkfat is made up of long-chain fatty acids, it also contains between 8 and 12 percent medium-chain fatty acids.

A better understanding of the energy sources in your milk or milk replacer will help you provide optimum nutrition for your calves. Remember, energy is a critical nutrient in young calf nutrition, but it must be fed at correct volume and in proper balance with fat and protein to provide optimal results.  PD

Tom Earleywine has a Ph.D. in dairy science from the University of Wisconsin – Madison and is director of nutritional services for Land O’Lakes Animal Milk Products. For more information, contact him by email or call (800) 618-6455.

Tom Earleywine
  • Tom Earleywine

  • Director of Nutritional Services
  • Land O’Lakes
  • Email Tom Earleywine