Summarize:

Body condition score is an especially good indicator of where particular individual cattle may be in the pecking order. Thinner cows may be the hard-keeper cows that need more energy and protein than the rest of the herd, but they may actually be those that are being bossed around too much and can't get the nutrients that they need for themselves. The fatter cows, too, may either the bossy cows or the easy keepers or both.  Cattle on the lower end of the pecking order tend to be less competitive for food than those that are considered the "boss" animals. The bigger bulls, bigger/stronger cows, more robust animals, etc. The "bossy" or "bully" cattle tend to come in when the weaker ones try to get at the feeder first to get what they can, and push those weaker cattle out so they can eat what they like until they are full. The lower-pecking-order cattle don't get what the need themselves, so become thinner than the bossier cattle. Separating the two groups into different pens can help remediate this.  Or, spreading feeding stations around may also help because it gives those lower down in the pecking order a chance to get what they need with lowered competition from the bovine bossies in the herd.
Take the pecking order into consideration.