I've given mine a hawthorn leaf each before since we have one in the garden but I'd avoid the branches because of the giant spikes.
@Swissgreys why would you avoid plums? I've given a very small piece to my boys once. I thought it was ok as a treat am I wrong?
No you aren't wrong - a small amount of flesh from a plum will not harm your boys.
Technically nor will a few leaves of cherry or plum trees as both
@Posyrose and
@Betsy have stated.
But this is a public forum, and anyone can read a piece of advice on here and take it out of context, so I tend to be quite conservative with my answers and sometimes a simplified 'blanket' answer of no is safer than a more complex answer.
Trees that produce stone fruit (such as plums and cherries) can have varing amounts (usually tiny) of cyanide in their leaves and bark as well as in the stones of their fruit. This ins't an exact science, but it is thought to occur in higher concentrations in older trees, but there aren't any precise figures for this (that I can find anyway).
So technically this could be dangerous when fed in large amounts, so the safest reply is avoid anything associated with stone fruit trees.
In all honesty I do occasionally feed my own pigges a leaf from the cherry tree in our garden, but if someone chooses to put an entire branch from a cherry tree in their piggies cage and the piggies later become ill, then I would look irresponsible for having said it's ok to feed cherry leaves.
The easiest reply is avoid anything associated with stone fruit trees and this can't be misinterpreted.
I hope this makes sense?