Wednesday, January 21, 2015 9:37 am

By BRUCE STEELMAN

Feed Levels for Cows During Winter

Beef producers have known that cow energy requirements increase in cold weather.

There is not much we can do about the weather; however adjustments in the diet of beef cows can reduce the effects of the winter weather.

Results from an experiment at Kansas State University suggest several advantages for adjusting energy levels for cold weather. This information was gathered during the 1979 - 1980 winter. The K-State researchers used 60 commercial cows fed in dry lot and fed one-half of the cows a steady diet based upon the thermal neutral requirements for body weight maintenance; the other 30 cows were fed a ration adjusted for 1% more feed for each degree of coldness.

Thermal neutral is generally considered to have its lower limits at 32 degrees wind chill index on cows with dry hair coats. For each 1 degree decrease in wind chill index, the feed would be increased 1%. Beef cows exposed to cold require more energy for maintenance therefore the results below indicate the effectiveness of making those adjustments.

There are several key implications from the results of this experiment. Cows that gained 115 pounds in the last 4.5 months of gestation should be in one full body condition score better at calving. This explains the increased cycling rate by 60 days after calving. In addition the 103 pound weight difference in the following fall indicates that the cows will go into the next winter in better body condition. The amount of additional feed (in the Kansas State study) to account for the cold weather events that winter would be equivalent to 125 pounds of corn per cow. The current prices of winter supplements must be considered when adjusting the ration to match the weather. HOWEVER, the expected continued high prices of calves in 2015 - 2016, means that every advantage to improve calf crop percentage or weaning weight should be utilized.

Source: Glen Selk, November 19, 2014. Oklahoma State University.

Cattle Care During Winter Weather
The long range weather forecast is calling for some extended cold temperatures. Over the course of winter cold temperatures, wind chill, snow, freezing rain and mud are all possible. All of these winter weather conditions can negatively impact livestock performance and in- crease the energy requirement of the animal.

- All animals have a thermo neutral zone, that is, a temperature range that is considered optimum for body maintenance, animal performance and health. The lower boundary of this zone is referred to as the lower critical temperature (LCT). Livestock experience cold stress below the LCT. An increase in the metabolism of the animal, generally by shivering, in or- der to maintain body temperature is one method of dealing with cold stress. This requires more energy, either from fat stores or more energy intake in the diet. The general rule of thumb is that energy intake must increase by 1% for each degree of cold below the LCT.

- As hair coat thickness is increased, the LCT decreases. For example, in cattle, the LCT temperature for a summer hair coat or a wet hair coat is 59 degrees F. The LCT temperature for a winter hair coat is 32 degrees F and for a heavy winter coat it is 18 degrees F.
- The producer needs to realize that once an animal's coat is wet, regardless of how heavy it is, the lower critical temperature increases to that summer hair coat LCT. This is because hair coats lose their insulating ability when wet. Sheep are the exception, since wool has the ability to shed water and maintain its insulating properties.
- Mud can also reduce the insulating ability of the hair coat. The relationship between mud and its effect on energy requirements is not as well defined, but depending upon the depth of the mud and how much matting of the hair coat it causes, energy requirements could in- crease 7 to 30% over dry conditions. In addition, there is research that suggests that mud may also be associated with decreased feed intake.
- Wind speed produces wind chill and can further increase energy requirements for cattle when those values are below the LCT.

Following are several management options to help cattle cope with winter weather stresses, including:
- Provide windbreak protection to reduce the effects of wind chill on energy requirements.
- Increase access to better quality forage. Cattle can increase intake to some extent under cold conditions and if forage is of good quality, then energy intake is also increased. Grinding poorer quality forages to decrease particle size can allow more intake and increased digestibility.
- Limited feeding of corn, or use of a high energy, non-starch feedstuff.
- Move livestock out of muddy conditions or take steps to reduce the mud by utilizing a feeding pad.
Source: OSU Extension Beef Team, Submitted by Jim Neel