How much do the energy requirements of cows increase during the cold weather? This depends on the magnitude of the cold, and if it occurs under dry or wet conditions. See the calculations below.
Under cold, dry conditions:
Lower critical temperature for a brood cow is 32°F under dry conditions. Below 32°F, daily energy requirements begin to increase. For every degree that the wind chill i below 32°F, a cow’s energy requirement increases by 1% (NRC, 2000).
Quick Math:
- Critical temperature is 32°F
- Determine wind chill from weather report:Wind chill on Feb 11. in Auburn: 25°F
- Calculate the magnitude of cold: 32 – 25° F = 7°
- Energy adjustment is 1% for each degree of difference
A 7% increase in energy supply is needed to overcome loss from the cold.
Under cold, wet conditions:
Lower critical temperature for a brood cow is 59°F under wet conditions. Below 59°F, daily energy requirements begin to increase. For every degree that the wind chill is below 59°F, a cow’s energy requirement increases by 2%.
Quick Math :
- Critical temperature is 59°F
- Determine the wind chill from weather report: Wind chill on Feb. 11 in Auburn: 25°F
- Calculate the magnitude of cold: 59°F-25°F = 34°F
- Energy adjustment is 2% for each degree of difference
A 68% increase in energy supply is needed to overcome loss from the cold.
Will feeding more hay meet the energy demands of my cow herd during cold weather?
Poor quality hay is unlikely to be sufficient to meet the energy requirements of a lactating brood cow under normal weather conditions (above 32°F). Even with increased dry matter intake (up to 30% more), energy requirements increase more than what can be supplied by low quality hay.
Using our “quick math” from above:
How can I overcome a large energy loss due to cold weather?
Do not rapidly change to a high-energy diet. Diet changes should be made gradually over time. Instead, provide a digestible energy supplement (i.e. soy hulls, dried distiller’s grains with solubles, corn, etc.) along with free choice hay during and after the cold event. Feeding a supplemental energy source for 3 to 5 days after the cold weather can help overcome losses.
Prepared by Kim Mullenix, Beef Production Systems Extension Specialist
