I know that most people won't agree, but personally, I beg to differ. If behavioural issues are caused by hormones (i.e. testosterone), how can removing the source of this not affect their behaviour?
I've seen behavioural changes in my boars after neutering.
I originally had a trio of boars, 1 already neutered, 2 not.
They started fighting to the point of drawing blood, (the two entire against the neutered) so the two entire were neutered in the hope of splitting them up and rearranging numbers to give them a sow each (this was a few years ago before I even knew boar dating existed!).
They were neutered, and very quickly all three were living in harmony. They were a very happy trio for about 2 and a half years, even with a then entire sow living in the cage directly next to them.
They were good until I moved house, and the two older ones (the one that was neutered before I got him and his brother) started picking on the younger one, no actual fighting, no biting or anything, but chasing him away from food etc. so bullied pig went off to live with my friends sows, and I have the two older ones living happily together again.
So yeah, slightly off on a tangent, but I definitely saw a change in their behaviour as a result of neutering.
