A thin cow with a BCS of 4, for example, could require 8% more energy than a cow in good condition (BCS 5) just to maintain body temperature at a temperature of 21°. Consider feeding thin cows slightly more energy to gain condition during the fall to early winter, so that they have lower energy needs during the rest of the winter.

Wet hair significantly increases the LCT, raising the critical temperature to 53° for a cow in good condition. In wet winters, especially with freezing rain, maintaining body condition becomes challenging, as cows expend extra energy to stay warm.

Wind increases heat loss, raising energy requirements. Providing windbreaks reduces energy needs by minimizing heat loss, helping cows maintain condition. For cows with wind protection, the ambient temperature can be used to estimate energy needs. Without wind protection, the wind chill temperature should be used to estimate energy needs.

Feeding cows during cold weather

To meet the energy needs of cattle during cold stress, it’s important not to make drastic changes to their daily rations, but to provide consistent, high-energy feed during extended cold spells. Over a week or two, feed more of the same ration or supplement with higher-quality hay, grains like corn, or energy-rich feeds like distillers’ grains (DGs). Good-quality forage or hay can also help, as the fermentation in the rumen adds internal heat to the animal.

When feeding lower-quality hay, grazing dormant range or grazing cornstalks, additional feed will be needed. One option is to feed a higher-quality hay source with higher total digestible nutrients (TDN), if available. Free-choice high-quality hay (58%-60% TDN) can work down to temperatures of 34° below the LCT of the cow (-15° for cows in good condition with dry hair or 19° with wet hair).

If cows are grazing cornstalks or winter range, supplementation with a high-energy feed may be desirable. While corn can be used to provide more energy, it comes with risk. Feeding more than 2-3 pounds (lb.) per head can decrease forage digestion, especially if the forage is lower in protein. Feeding corn with some alfalfa on low-protein forages can mitigate this issue.

For corn supplementation, 3 lb. of corn (82% TDN) provides 2.5 lb. of TDN, which can offset energy requirements for a cow (BCS 5) down to 5° with a dry coat or 38° with a wet coat.

DGs are another excellent choice — both high in energy and protein. DGs can reduce forage substitution effects. Compared to corn, the decision to feed DGs leans more toward cost than digestion limitations. In the case of DGs and gestating cows, the pounds of TDN needed to account for energy used due to cold stress would be equal to the pounds of dry distillers’ that would need to be fed daily.

When wind chill temperatures are extremely cold or the cow has a wet hair coat, a lot of supplement would be needed to make up the greater energy needs and maintain body condition. For instance, if the wind chill was -10° and the cows had a wet hair coat, then 8.9 lb. of dry distillers’ would be needed to account for the increased energy requirement.

However, feeding these levels can be impractical. A better approach would be to provide a smaller amount of supplemental feed and to continue to feed the extra feed after the weather has moderated to allow cows to regain energy lost during the storm.

Remember, lactating cows have a much greater energy requirement than pregnant cows. The combination of cold stress and lactation can pull down BCS quickly.

For lactating cows, the energy demand is even greater, and cold stress can have a more immediate effect on body condition. Ensuring that these cows have adequate nutrition before they start losing condition is key to preventing further complications, particularly during the harshest months of winter.

How to calculate extra energy needs for cows

You will need to gather this information to figure the extra energy needs:

• the cow’s LCT (based on her BCS)
• the outside temperature (ambient temperature) if a windbreak is provided or the windchill temperature if no windbreak is provided

Using a cow’s LCT, you can figure the percent increase in energy based on the outside temperature. Use the wind chill temperature if there is no wind protection. If there is wind protection, use the ambient temperature in the formula.

There is a 1% increase in energy need for every 1° below the LCT.

Let’s assume a cow is in BCS 5. The BCS 5 cow’s LCT is 19°. For this example, let’s assume the ambient temperature is 21° and the wind speed is 10 mph, which makes it feel like 11° (the wind chill index).

No windbreaks:

• LCT – wind chill index = % increase in energy requirement
• For our example: 19 – 11 = 8% increase in energy requirement for a cow in good condition (BCS 5) with a dry winter coat

If a windbreak is provided:

• LCT – ambient temperature = % increase in energy requirement
• For this example: 19 – 21 = No increase in requirements for a good condition cow (BCS 5) with a dry winter coat

The energy needs of various classes of cattle can be found here. A 1,200-lb. dry cow in late gestation has an energy requirement of 13 lb. TDN. The cold described above in the no-windbreak situation increased this need by an additional 8%, which is equal to 1 lb. of TDN, for a total of 14 lb. TDN per day.

Conclusion

Proactive management during cold weather is essential to reduce cold stress in cattle. Monitor body condition, provide wind and moisture protection, and adjust feed to meet increased energy needs. Ensuring cows are in good condition before winter and supplementing their diets as necessary will help maintain herd health and productivity through the cold months.

Editor’s note: Bethany Johnston is a Nebraska Extension educator. Karla Wilke is a cow-calf systems and stocker management specialist for the University of Nebraska. Mary Drewnoski is a Nebraska Extension beef systems specialist.

Angus Beef Bulletin EXTRA, Vol. 16, No. 12-A