A horse’s shoes, bits and saddle all contain metal parts. You may not have considered the health risks associated with this, but if any parts of your horse’s body are impacted negatively by poorly-fitting metal parts, it will almost certainly cause “inappropriate” behavior.
If the horse is shod, metal will obviously be used in the shoes, although more and more riders are opting to go barefoot, given the seemingly recent recognition of the inherent sensitivity of the hoof (which seems so commonsense to me since the horse’s hoof is analogous to our middle fingernail!). But, like many others, I used to shoe my horse regularly every six to eight weeks when I was competing, and felt I was doing the right thing to protect his feet.
The second area is in the mouth. A metal bit is considered part of the bridle and can be used for gentle control in proper training – or, conversely, if used incorrectly and in the wrong hands, can actually become an instrument of torture. Like many others who have negatively impacted their horse’s mouth, I was probably responsible for the iron mouth my first pony developed because I didn’t use the right bit, nor did I use it properly. I now greatly admire the control that can be gained by simply using hackamores without any metal at all in the mouth – especially when one considers the various reflex points in the head. It’s not known who invented the first bits, or when and where they initially appeared, but presumably around 4000 BC when horses were domesticated, the first attempt at “control” was made using bone or wood in the mouth. Metal bits came along much, much later.
The third place where metal is used is in the saddle – the gullet plate and spring steel are both used to give the saddle more stability and help it protect both horse and rider from longterm damage – if and only if the saddle is made and fitted properly. The spring steel gives the saddle support along its length and needs to be customized to fit the rider: longer and thicker for the heavier rider, and shorter and thinner for a lighter rider. The gullet plate is only truly adjustable in some saddle brands – usually it gives stability to the saddle at the pommel to maintain the proper width of the tree over the wither area, but essentially it should be able to adjust to accommodate inherent asymmetry in this area of the horse.
In short, there is a valid reason for all these metal parts – if they are fitted properly and used as intended. Each of the three areas that traditionally incorporate the use of metal plays a crucial role in the horse’s health and well-being. And each of these areas, if impacted negatively by poorly-fitting metal parts, will almost certainly cause “inappropriate” behavior.