Combat cold stress with quality forage

Almost every region of the United States saw record-high temperatures in December, but the extended forecast calls for much colder conditions. With artic air sweeping across the central states, it will be vital to feed high-quality forage and supplement cattle diets to meet animals’ elevated energy needs.

Cold stress in cows creates a snowball effect as animals expend more energy to keep warm. This leads to lower body condition scores, which can result in weaker calves and unsuccessful rebreeding. The threshold for which cold stress begins depends on cows’ lower critical temperature (LCT).

Mary Drewnoski and Karla Wilke at the University of Nebraska Extension explain that cows with good body condition and a heavy, dry winter coat should be able to maintain their body temperature until the wind chill index is below 19°F. Then, the beef systems specialists say subtracting the wind chill index from cows’ LCT will equal animals’ additional energy requirements.

“There is a 1% increase in energy needs for every 1°F below the LCT,” the extension specialists state. For example, a cow with an LCT of 19°F minus a wind chill index of 11°F would result in an 8% uptick in the animal’s energy needs.

Cows with lower body condition or thin winter coats will have a higher LCT, which means animals will start using energy to maintain body temperatures sooner. A wet coat will reduce a cow’s ability to stay warm much more significantly. In fact, the extension specialists say the LCT of a cow in good condition soars to roughly 53°F.

Target TDN

Regardless of a cow’s LCT, feeding high-quality hay during a cold snap will help ensure animals have enough energy to meet their needs. The extension specialists recommend targeting forage with 58% to 60% total digestible nutrients (TDN). Feeding a greater amount of lower quality hay may provide some added energy, but cow intakes will eventually become limited.

If cattle are grazing winter pastures, the extension specialist recommend feeding a high energy supplement. Corn grain is one option; however, too much corn can negatively affect the rumen. With that said, feeding alfalfa hay with corn could mitigate this issue.

Feeding dried distillers grains may be a more viable option. The extension specialists suggest providing 1 pound of dried distillers grains for every additional pound of TDN required to meet animals’ energy demands under cold stress.

“Distillers grains are a good source of energy. They have more energy than corn, and because they are high in protein, they do not cause as much of a substitution effect,” the extension specialists note. “Limitations on the amount of distillers grains that could be fed would be more based on budgetary concerns rather than digestive effects.”

If the wind chill is low enough, or if cows have wet hair coats, energy demands may be too high to achieve with high-quality forage or supplemental feed. In this case, the extension specialists encourage producers to continue providing extra energy after temperatures warm up to allow cows to regain body condition that was lost during the cold weather.

Moreover, lactating cows inherently have greater energy requirements than dry cows. The extension specialists say body condition can decline much faster in lactating cows under cold stress, so managing their energy intake is even more critical.