horse showing bad behavior to my daughter

Question
I have owned our horse since he was 6 months old. he is now 5 1/2. He is quarter horse x. I have been the person to handle him and do the ground work but my children have always been around him. After he was broken in i was the one who rode him as my daughter had a beautiful Crabbet Arab. We then moved, sold the Arab and for the last 12months he has been in a agistment paddock with about 18 other horses. Also my daughter has been ridding him for the last 6 months. He started to show some nastiness towards her ears back, nostrils flared, so i suggested i don't ride him and just let her, then he started not coming when called ( in the past he would) then turning his backside at her and now turns to bite her but never followed through. My daughter is 12 and can handle her self really well around him which is good but he never used to be like this, and he was a lovely kind natured horse, she loves him and wants to continue riding him but i'm at a loss as to want to do about this. Also his feed is basic over the years i've found the following to work best. chaff (Lucerne mixed with wheaten), mitavit xcool pellets, garlic and a mineral powder. but i let the local produce store talk me into replacing the xcool with a complete feed called AG AM. any advice would be great  i understand our feed might be different as i'm in Australia.

Answer
Ronnie,

You have a horse who is now in a herd environment so he's had to establish his ranking in the herd.  You are an adult, have always been one as long as he's known you so your dominance is recognized.  Your daughter, on the other hand, is a child and he is totally disrespecting her.  She's going to have to establish a different relationship with him; he has to acknowledge that she, too, is is superior and is to be respected.  He's young, so you are essentially dealing with a teenaged bad-boy who's running with a gang.  Same sort of mentality in horse herds.  If his is a mixed sex herd, there's even more pressures on him.  In the horse world, the girls run the show.  The true leader of the band is the lead mare.  The stallion is subject to her wishes.  She decides when and where the herd moves, when to go to water, all the mundane everyday functions.  When the herd moves the mare is the leader, the stallion follows behind primarily to keep the stragglers moving and protect the rear.  Sometimes a stallion will let his sons hang with the herd until they start to show an interest in the mares.  If they behave themselves they can stay a while.  But herds of just boys are like gangs of human boys.  They play rough, most will bear battle damage, and there is a definate leader of the pack.  

Your best solution to this is round pen work.   I would start with both of you in there, and go from there to her alone.  If you aren't familiar with round pen work there are a number of guys down there that are excellent with the round pen and natural horsemanship.  There are lots of good books on it and better yet, videos.  It would also be necessary for your daughter to watch/read too so that she knows what she has to do.  Pat Parelli has some excellent ones and it's better to actually watch it vs. read about it.  Maybe you could even find a clinic.  It will straighten him out with an attitude adjustment that will stick.  

Let me know how it goes.

Lyn