Why not just show them being slaughtered? I mean, its life, right? Make an abbatoir exhibit. 'This is how we feed our animals'.
Its about context. If you have a meaningful farm exhibit for domestic stock showing their roles in human civilizations, for example at Drusillas (and this is a zoo aimed at children), as opposed to 'familiar friends', 'Pets corner', 'children's zoo' etc, then it is easier to imply that those animals the visitors see may go on to become true farm livestock........I think whether that is at another site or at the zoo itself is slightly irrelevant as long as the animals are displayed in such a context that does not suggest they are 'pets' or different in any way from farm livestock.
However, I think zoos do well to use abbatoirs that have to meet external standards, rather than run a cheaper operation of slaughtering their stock on site.
As for non-domestic species, I think the message gets extremely messy when antelope or deer etc are found to be fed to carnivores when surplus to requirements. Also, non-domestic species, unless shot, are likely to find the process of being brought to an abbatoir or to a small shed or pen for slaughtering far, far more stressful than for domestic stock, which on the whole are more used to being routinely moved and transported short distances by humans.
I don't believe the general public cannot accept that carnivores eat domestic animals that were once alive. I think zoos run into trouble when their boundaries around this issue and the roles of their stock are not made clear.