Two years ago we purchased a five-year-old PRE (Andalusian) stallion here in Nicaragua, where we live. With intentions of building our own barn in the near future, we kept him at a location where the accommodations left a lot to be desired, but sufficed. Over the course of a few months he eventually stopped eating and basically went a little crazy (weaving, not drinking, constantly climbing into his feeder and scraping his legs, etc.) He lost several hundred pounds, so we sent him back to the farm where we bought him from to regain the weight and be taken care of by the handler he was used to. Slowly but surely he regained sanity and health, while we built a beautiful stable for him and the three foals we had also purchased. The stallion has always been a bit aggressive on the ground, but the man we have working at our barn handles him well and everything was fine.

In January we purchased another stallion (12 years old) and a mare from the same place and brought them to our barn. Over time, the two stallions have developed quite a hatred for each other, as well as possessiveness over the mares on their respective sides of the barn. We recently put in two beautiful fields where we put all the mares out together, which caused an unexpected ruckus. If the 12-year-old stallion can’t see his mare he gets upset and then he quickly forgets about it, but if the younger stallion can’t see his mares he would get absolutely dangerously crazy (running the fence or in his stall, weaving at the speed of light, calling continuously, etc.). This was a few weeks ago and has calmed down to normal since then.

However, the stallions’ hatred for each other has significantly amplified since then, to the point that the older stallion viciously kicks his door every time the younger stallion walks by and he will try to charge at the other in the sand ring while we are riding. He will Spanish walk and passage around the ring for the first 20 minutes when we ride with the other stallion, but he respects people and responds well to an authoritative voice and some reprimands. The younger stallion is generally lazier and just makes mean faces, but is more aggressive on the ground. We have been very effective in controlling that until yesterday when the younger stallion threw himself to the ground to attack the front legs of the other stallion, while both were being ridden by extremely experienced riders. Both horses went to the ground (and both riders abandoned ship) and fought briefly, until one of the riders got a hold of the younger stallion and got him out of the ring and closed the gate behind them. *Phew* Crisis averted…UNTIL the older stallion rushed up to the gate and broke it down to get to his adversary. Both stallions were loose and fighting each other on the ground for less then a minute, until the same rider grabbed the younger stallion again and got him away.
The younger stallion is quite beat up, including a huge bite on his throat and a lot of cuts, but the older stallion is fine. This was totally initiated by the mentally unstable younger stallion, but the older stallion has been bringing this on for a while, by acting so aggressive (but controllable) toward the other.

We went into younger stallion’s stall last night to check on his wounds and he tried to attack us at the door. He was fine once he was being held, but tried to attack again as soon as we let go. His aggression has reached a point where we are prepared to try anything to deal with it. He is so unpredictable and sometimes insane that we aren’t sure how to deal with it. Normal stallion-handling techniques are clearly not working. We clearly need to deal with the problem (for both stallions) much more harshly and effectively than we have done thus far.

Any suggestions?

You have alot going on.
While breeding may sound like a good idea, it seems that you are overfaced.

Andalusians are not an aggressive breed in general, I have dealt w/ both them and Lipizzans.

If yours are to this point;
1-It is not a lineage that should be reproducing.
There is nothing about these two horses that is so outstanding that they should be used as breeding Stallions.
That is a trait that a breeder should take due diligence to extricate from the breed itself.

Not easy to hear-but the first Stallion did not thrive in your care and became a much better animal when returned to the breeder.
That pretty much sums it up.

Bringing another Stallion in, should not by itself cause anything like what you are seeing.

There are thousands of facilities throughout the world called Stallion stations, which are exactly that.
A facility which houses and breeds Stallions.
Each of these animals no matter what breed, are extremely well behaved animals who perform their job-to breed. QUIET and SAFELY.

Again, knowing what you do.
It was complete negligence to have those two animals in the ring @ the same time.

Why don't you-Keep the mares and either send out or have semen shipped in.
You still get to breed, have babies and a business if thats your goal.
And everyone will be alot safer.

I generally breed or own aqha's or apha's but have owned a variety, and I will NEVER keep a stallion that is aggressive towards humans.
These two being aggressive towards one another is no surprise - they are stallions, and when mares are present or nearby, aggressive behavior shouldn't be a shock. Though your stallions do sound quite excessive. (and both in the ring at the same time is a mistake if they are that unmanageable).

I would definitely say geld one, or sell one. One tip I have to keep in mind however - if you are going to keep stallions, can you keep them on pasture turn-out? And especially with their own mares. After breeding season I always turn my stallion in with his own mares for the following summer/fall/winter. This makes him MUCH MUCH happier and content as an old range gelding.
Even if not with mares, pasture turn out alone, or with an active gelding or two really helps the attitude of a stallion. My motto is, if they cannot be pastured out most of the time, either with their own mares, or geldings, they shouldn't be stallions. There are far too many great stallions out there that are extremely manageable that one shouldn't have to own one that is excessively aggressive.

Also of course, grain accelerates a horse's energy and active behavior - I don't generally grain my stallions unless it is winter time, or if I am working them. I do realize though the bigger operations generally grain their stallion(s) even when not working; I don't see any great point to this because they are much easier to be handled when not on a ton of high protein feeds.

Hope my 2 cents helps Good luck and DON'T get hurt. NOT worth the risk.