Dr. Glenn Selk, Oklahoma State University
Drover’s Cattle Network, November 19, 2014
Beef cow nutritionists 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 the range beef cows can mitigate the effects of the winter weather.
Many years ago, a northern Oklahoma rancher told about his method of maintaining body condition on fall-calving cows during the course of the winter. He watched the weather forecasts closely and increased the amount of supplement that he fed to the cows for about one day before a winter weather event and during the winter storm. Then he would return the supplement pattern back to pre-storm levels when the weather returned more to normal. For example, if he was feeding 5 pounds of a 20% range cube, he would increase that to 7 pounds per head during the wet, cold spell. Then he would return the level to 5 pounds when the weather returns to normal. Of course, his cattle had free-choice access to adequate standing native forage or grass hay. Note that cow size may require that supplement levels need to be adjusted accordingly. (This rancher had moderate sized 1100-pound cows in the 1970’s when this was his “rule of thumb”.)
Research about this subject bears out this rancher’s observations. (See Table 1 below.) 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.
|Table 1. Impact of adjusting winter ration for changes in weather|
|Ration Adjusted for Coldness||Ration NOT Adjusted|
|Weight change during last 4.5 months gestation||+115 pounds||+26 pounds|
|Weight change from fall to following fall at weaning||+10 pounds||-93 pounds|
|Percent cycling by 60 days after calving date||82%||65%|
|Estimated date of conception in subsequent breeding season||June 5||June 15|
|Ames, D.R. 1981. “Weather, what can you do about it?” in Western Beef Symposium October 26-27, 1981. Boise, Idaho|
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 feed 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.