Environment, body size impact winter calf nutrition

Care given to dairy cattle needs to change in the winter to meet the animals’ higher maintenance requirements.

“Calves are particularly susceptible to cold stress, especially during the first three to four weeks of age before they begin consuming measurable quantities of calf-starter grain,” says J.W. Schroeder, North Dakota State University Extension Service dairy specialist.

Calves lose body heat much more quickly than larger animals, which have a larger surface area. The smaller the calf, the more important this relationship becomes. For example, research shows that small calves, such as Jerseys, had a maintenance requirement at least 15 percent higher than large-breed calves such as Holsteins.

The environment also has a significant impact on maintenance requirements. During the winter, calves require deep, dry bedding to help them maintain the insulating capabilities of their hair coat. A wet environment with limited bedding greatly enhances heat loss.

Third, calves are born with relatively low reserves of body fat that they can mobilize during periods of low energy intake or environmental stress. The following example of a calf weighing 100 pounds demonstrates the impact of cold weather on nutrient requirements:

• At 68 F, feeding 1 gallon of a milk replacer with 20 percent fat provides enough energy for about 0.5 pound of daily gain.
• When the temperature drops to 41 F, 4 quarts of milk replacer is just enough to meet the calf’s maintenance requirements with nothing left for growth.
• If the milk replacer has only 15 percent fat, then 4 quarts of milk replacer is sufficient for maintenance at 50 F.

“So timely feeding is paramount for calf growth and development,” Schroeder says. “However, another stress occurs, even though most calves are fed equal amounts early in the morning and again later in the afternoon. The nutritional stress occurs during the long interval between the evening and morning feeding, when the temperature drops after sunset. Based on the calves’ requirements just to stay warm, the need to increase calf feeding rates during the winter is obvious.”

Researchers recommend a 20 percent fat milk replacer rather than those with lower fat content. Calf-rearing experts also suggest increasing feeding rates by 50 percent or even doubling them in extreme cold conditions. In the winter, 4 quarts is not enough.

Feeding 1.5 gallons of a 20 percent fat milk replacer reconstituted to 12.5 percent solids provides sufficient energy for 0.23 pound of gain at 32 F. However, maintaining a growth rate of 0.4 pound at 20 F would take 2 gallons of this liquid.

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