Calves that are younger than three weeks of age have a larger surface area relative to their body weight and may not be able to withstand changes in environmental temperature as well as older calves. These younger calves may need additional energy beginning at environmental temperatures as high as 59° F. Keep in mind that each calf is different and no one temperature describes all calves or all situations. Exposure to wind, sun and moisture as well as bedding and housing all influence how environmental temperature affects calves.
Feeding options used to increase energy intake through milk and milk replacer include:
- increasing the volume of fed
- utilizing a higher fat milk replacer
- adding more milk replacer powder
- adding a high energy supplement.
This post will explore these changes in energy and effects on solids (concentration) of milk or milk replacer.
When the environmental temperature falls to 30° F, the calf needs about 25% more energy than at 50° F. As the temperature drops to 10° F it needs 50% more energy. The table below shows the energy provided by one ounce of milk replacer that's formulated to 20 percent protein and three different fat levels. The energy provided by a 7-60 high fat energy supplement is also shown. Values are on a dry matter basis.
Milk Replacer and 7-60 Energy Supplement
The total energy in a feed is a combination of the energy from the protein, fat and carbohydrates contained in the feed. As seen in the table, using a milk replacer with a higher fat percentage does not increase the overall energy by very much. Simply switching to a higher fat milk replacer during cold weather and feeding at the regular rate, will probably fall short of the calf's increasing energy need during cold stress -- maybe by a lot.
The 7-60 in the table is a high fat energy supplement, providing 7% protein and 60% fat. This energy supplement provides about 30% more energy than milk replacer.
The higher energy density of the 7-60 energy supplement makes it possible to increase energy consumption without increasing solids as much as what occurs when increasing the concentration of milk replacer powder in water. Table 2 shows what happens to solids when you add more milk replacer powder or use an energy supplement to meet the calf's increasing need for energy.
The left column lists three levels of powder commonly used when mixing milk replacer. The solids levels of the mixtures are provided in the next column. For example, when you feed 8 oz of powder and increase the energy by 25%, you would use 10 oz of powder, which results in solids at 14.5%.
A 50% increase in energy requires 12 oz of powder at a solids level of 17%. Meeting these energy needs with the 7-60 energy supplement lowers the final solids to 13.5 and 15.5%, respectively. You can also see what happens when your normally feeding rate is 10 oz and 12 oz of powder and you increase the concentration of powder.
Solids levels of 17-18% are often used with intensive milk replacer feeding programs. Calves should be able to adjust to this feeding level. But when you get into the 20-24% solids range, the likelihood of causing digestive issues increases. Highly concentrated milk replacer, especially when fed in large volumes, pulls water from the calf into the digestive tract and may ultimately lead to scours and dehydration. If you choose to feed at higher solids, access to clean water is a must.
As the tables demonstrate, a high fat energy supplement may offer an advantage when solids are being altered to meet the calf's energy needs. The table also shows that there are situations where it is better to simply feed more of the regularly concentrated milk replacer rather than concentrating it. You can either feed more at each feeding or add another feeding during the day.
Calves that are older than three weeks of age should be eating a significant amount of starter and can offset much of their need for energy during cold stress through increased starter intake. Access to water is a necessity for increasing starter intake.
Calves that are younger than 3 weeks of age are more dependent on milk or milk replacer for meeting their energy and protein needs. Very young calves may have difficulty consuming all of the energy they need during cold stress through increasing consumption of milk and milk replacer. Some calf raisers extend colostrum feeding to help improve the level of nutrient intake of these calves. Compared to the values in Table 1, the average energy value of one ounce of colostrum is about 185 kcal. In any case, you may need to go beyond a strictly nutritional solution and actually reduce the effect of lower environmental temperatures on these young calves by using tools such as calf coats which can greatly increase the calf's insulation against cold temperatures.