Red clover can cause 'stallion-like' behaviour in geldings.
The first line of thinking when such behaviour shows up is that the horse hasn't been gelded properly. However in most cases blood tests indicate otherwise. They have indeed been thoroughly castrated and the behaviour has a much simpler explanation: there is red clover in their pasture grass.
Red clover is slower to flower than white clover. About now is when its red flowers become very visible in pastures around NZ. There are several ways it can cause problems in horses.
This particular experience caused a few ‘pennies to drop’....
A while ago I bought a very quiet little gelding off a woman who had to leave the country because her Visa was due to expire. She had ridden this horse all the way ‘up’ the South Island of NZ, through all the High Country stations. That is quite a trek! I was keen to buy him because I knew of a teenage girl who was looking for such a quiet gelding. She came over and stayed with us for 5 days while she tried him out to make sure he was going to suit. Then he went home to her place which was some two hours away. Everybody was happy! Two weeks later I get a call: “He has turned into a stallion!!” She related how he had run through the fence to attack when another horse was led along the road adjacent to his paddock! When the vet came to stitch him up he was ‘front-footed’ by him! It was hard to believe this little horse had changed so much in just two weeks! Needless to say I hurried over there to see what was going on.
As soon as I saw the property the problem was obvious: the ‘pasture’ consisted of 100% RED CLOVER. The property had been used in the past for growing red clover seed. It turns out the reason the parents wanted a gelding this time for their daughter was because they already had two mares out in the back field that no-one could do anything with because they were so ‘hormonal’ and dangerous to be around. Fortunately a friend of theirs lived just down the road and offered to put the little gelding in his round-pen on grass hay. About five days later he was back to his lovely quiet self again.
In the end the family had to move properties because it was not possible to successfully keep any horses there. Sure, this was an ‘extreme’ case but for every ‘extreme’ case there are hundreds of ‘mild to moderate’ cases.
Clovers are legumes not grasses. Aside from their mineral imbalances and photodynamic pigments (which cause mud-fever and sun-burn), they also contain ‘hormonally active compounds’ (phyto-estrogens) which can affect both geldings and mares.
Geldings become uncharacteristically ‘aggressive’, mount mares or ‘hound’ their paddock-mates sometimes relentlessly. Anyone who has witnessed this ‘behaviour’ knows what we mean, we have had horses over the years who have done ALL these things, even resulting in injury and large vet bills.
Fortunately, for most horses showing symptoms like this, once you have meticulously removed ALL legumes from their diet, these ‘behaviours’ just disappear and are never seen again. I don't have photos of the little gelding but these photos are of 'Jack' another horse we rescued when he was going for dog-tucker because he was deemed 'too aggressive'. He also had chronic mud-fever.
The the picture above is of the paddock he was grazing when we got the call for help. He has been a wonderful, quiet riding hack and therapy horse ever since!
This is why we don't recommend sowing red clover into your horse paddocks, after seeding a few years it will become more abundant and cause problems for your horses. If you see you do have red clover in your paddocks one way to deal with it is to borrow some sheep - just for long enough for them to nip out the clover. As with all clovers, the best way to deal with it is to annually - in early spring, go over your paddocks with a broadleaf spray. If you are worried about the environmental affect of this, please read through Nitrogen & Clover