We've always been very open with the kids about what meat is made of. English likes its meat euphemisms like pork, and beef.
I remember Anna, before she could speak properly, used to differentiate using the animal noises - we had cluck-cluck meat, moo-meat and oink-oink meat.
Yesterday, completely seriously, after a meal out with his school friends, Léon asked me what breed of dog was used in hot dogs! He even looked a little deceived when I mentioned they were unlikely to contain dog (though there might be the odd chunk of horse in there, depending on where they were sourced ;-) ) I'm sure my doggy-loving mates will be horrified, but he'll never have any issues with intercontinental travel, that's for sure.