If the horse gets grabby for food then it must be the fault of the food (form; dimensions, calorific value etc), right? So the solution is to change the food in some way (different type of food, or change what the food looks like or how it has to be handled by the horse, e.g. harder for the horse to pick up so they have to be more careful, make the horse chew more) to make it harder for the horse to show the grabby (or other unwanted behaviour) behaviour, right?
There is a huge assumption there that it is the type, or form, of food that is maintaining the unwanted behaviour. And of course changing the type/form of food might make the behaviour go away. But that does not mean it’s a property of the food itself that was maintaining the behaviour.
It could have been one or more of the other variables of the combination of operant cycles working alongside each other that was maintaining the behaviour. The horse is not behaving in isolation…the environment, including the variations of the behaviour that we have inadvertently reinforced in the past, etc, all play a part. The horse is influenced by the operant cycle we are in as a handler.