FWIW
Most of the larger feedyards are in W Kansas, Ok & Tx where the usual humidity is much lower. However, there are a very few times where there the humidity is much higher than normal and wind speed is less than normal which can result in these extreme conditions. Most of the feedyards that I am familiar with do have sprinklers. When the humidity is high and there is little wind, running the sprinklers does not cool the air like it would in more favorable circumstances. These are extrordinary conditions that no amount of preparation can totally manage. You can put it in the same category as blizzards, ice storms and flooding. There is no way to totally eliminate the effects of mother nature upon anything with magnitude of exposure.
The milder winter, lower rainfall/humidity are the main reasons the cattle feeding industry moved from the midwest to the southern plains. On a year around basis, cattle gain more efficiently in these areas.
Regarding changing rations. We are talking of many yards that feed 50,000+ plus head at a time and the rations have very high grain content as this is what gets the fastest and most important, lowest cost of gain. When feeding these high starch rations, much care has to be taken anytime a ration change is made. If ration change is made too rapidly, you can get into a major wreck that is spelled in $$$$$$$$. All of the yards use a professional nutritionist and no ration changes are made unless it is coordinated with the consulting nutritionist.
Although they may seem to be simple operations. An large, efficient feeding operation has a lot of very technical variables. Like most everything in our world, cattle feeding has become very high tech, yet is still at the mercy of mother nature.
Hope this has clarified some misperceptions.