Horse Herd Behavior: www.thinklikeahorse.org

Question
I board my 3 horses at a barn where many other people have their horses too. There are about 15 head of horses there and all of the horses have made themselves into groups kind of like a popularity list. My horse Zeke is at the top. He is pretty much the boss of the herd and is always with everyone. I went to visit him today and he was all alone. he wouldn't eat the apple i tried giving him and only took one or two horse treats. My others horses were following me for more treats. he usually would but he didn't. he just stayed away. I went up to him and the other horses followed me and chased Zeke away. If Zeke got within maybe a few feet of any other horse he would get kicked or chased away. Zeke might kick but isn't fighting back like he usually does. this is worrying me. i heard that if this happens the other horses might sense something like he is sick and they don't want him around. is there anyway you can tell from my explanation that he might be sick or that something is wrong based on how all the other horses are treating him? he is completely alone and will not go near anyone and wouldn't eat anything i tried giving him. i wish i could spend more time with him today but i had to leave..

Answer
It could be lots of things, he could be sick, he could be hurt, if a lead horse gets a bad leg or other injury, the others horses know it and know that he is no longer the strongest leader so they take over.  If a lead horse can't defend or hold on to his position as leader, another horse will take over, it is their instinct and how they ensure the success of the herd.  So it could lots of things, but something changed.  So he could be old and knows he can't fight off the young guys, he could have an injury, he could be sick or could have gotten beat down by a younger horse (it does not sound like this).  My guess would be he is sick or injured, not eating is not good and could be colic, I would be checking on him and if it is colic watch him closely or he could die.  Colic is number one killer of horses and change in demeanor, not eating are two of the possible symptoms.