Preparing the cow herd for cold weather

As a risk management strategy at the ranch level going into the winter, reduce the number of BCS 4 cows and increase the number of BCS 5 cows in your herd.

Rick Rasby

Another management strategy is to provide cattle with an area that provides wind protection. The lower critical temperature of a beef cow is the lowest temperature a cow can be exposed to before she needs to have changes metabolically to help her cope with cold stress.

Usually what happens metabolically is: Cows begin to shiver. These processes require extra energy. Lower critical temperature for beef cows is influenced by hair coat condition (dry or wet/muddy), body condition (thin, moderate, fleshy) and hair coat description (heavy/winter) – winter, fall or summer.

As hair coat changes from summer to winter, BCS changes from thin to fleshy and hair coat changes from dry to wet, lower critical temperature decreases, which means cows can withstand harsher conditions without an increase in energy needs.

Magnitude of coldness is equal to lower critical temperature – wind chill index. Energy requirements increase about 1 percent for each degree of cold stress. As an example, cows with a heavy winter hair coat that is dry and are in condition score of 5 have a lower critical temperature of 19ºF.

Energy needs of the herd

Let’s say that for the next week, temperature is going to be 5ºF and the wind out of the north at 15 mph; then the wind chill index is -10ºF. At those environmental conditions, energy needs of the herd increases by about 30 percent.

If the total digestible nutrients (TDN) requirements of the cows are 12 pounds of TDN per head per day for this week, you would consider bumping the ration to 15.5 pounds per head per day. This is an increase in 3.5 pounds of TDN per head per day.
If grass hay is 57 percent TDN, that’s an increase of about 6 pounds per head per day on a dry matter basis.
If the hay is 88 percent dry matter, that would mean each cow receives an additional 7 pounds per head per day.

If these cows were being fed 24 pounds per head per day under current condition, could they eat 31 pounds per head per day during the harsh weather conditions? For a 1,200-pound cow, this calculates to about 2.3 percent of her bodyweight on a dry matter basis – so, yes.

Be very careful if you plan to use grains (corn) to increase the energy density of the diet during severe conditions, as you may do more harm than good. Feeding more than 2 to 3 pounds per head per day of corn to cows on a forage-based diet will decrease fiber digestion.

When cows are on a forage-based diet and supplemental energy is needed, consider the use of high-energy, non-starch feedstuffs such as distillers grains and soyhulls to meet cow energy requirements.

It would not be advisable to change rations daily, but if it is predicted that weather conditions will be severe over a period of time, then ration changes may be warranted.

Pro-active approach

The pro-active approach would be to have cows in adequate body condition and provide shelter belts in winter.

Sometimes weather conditions are so severe that cattle cannot be fed enough to meet the increase in energy needs. In these conditions, getting feed to them is the best that can be done. These extreme conditions usually don’t last for a long period of time, but the effects may.

Checklist

1. Economically manage feeding programs so cows enter the winter in BCS 5 or greater.

2. Develop shelter belts for cows to protect them from high winds.

3. If weather conditions are going to be severe for extended periods of time, be prepared to feed more energy to cows.

A webinar titled “Caring for Cattle in Cold Weather” highlights the effects of cold weather on cattle and management practices to help mitigate these effects.