Well, more aimed at a general audience than YA (but who knows what publishers will classify it as) my MC's about 14 or so (it's set 40,000 years ago so they don't count their ages like industrial people do) and he kills and eats animals for food. Anyone who's uncomfortable with the fact that hunter-gatherers need to hunt and eat animals probably shouldn't be reading books about hunter-gatherers to start with and 40,000 years ago, everyone was a hunter-gatherer, so I don't really care if anyone's disturbed by it.
Regarding sentience, the current scientific evidence suggests that all land vertebrates (birds, mammals, reptiles*) are sentient, as are some cephalopods (squids/octopus) and some insects (fruit flies are the only ones I recall being named but it's likely that there are a lot of other sentient insects). Additionally, there may be other animals that are sentient besides those, but those are the ones that scientists are pretty sure about. So I would struggle with the idea that "it was just like eating chicken, but then I found out it was sentient" because chickens are sentient. They're also quite a bit cleverer than they're given credit for, albeit not in the same league as ravens and parrots - which are possibly as intelligent as chimps.
*I don't remember if they classified amphibians as land vertebrates or not
Perhaps you mean sapient rather than sentient. Sentience means self-aware and able to feel fear, pain and pleasure and choose to flee from bad scary things and seek out nice, pleasurable things. It doesn't involve an ability to reason beyond "aagh scary" (runs away) and "mm nice" (goes towards it) - but awareness as yourself as an individual that can be hurt is necessary to have that level of reasoning. (Note that scientist distinguish between actual decision making versus reflex actions, and the animals named have shown evidence of decision making rather than acting on reflex. There's more to sentience than just this but I'm trying to keep the post short.)
Sapience isn't so clearly defined but usually meant as human-like levels of intelligence. Great apes* (humans are a species of great ape) have a higher level of cognition that involves recognising each other as individuals, the ability to understand past, present and future and understand the consequences of their actions, make plans, understand complex social interactions, etc. I'm a supporter of
great ape personhood. (More details about the intelligence level of non-human great apes in that article.)
*and probably various other highly intelligent species such as corvids (bird genus that includes ravens), parrots, elephants, dolpins, whales and maybe a few other animals - I don't know as much about these as great apes but have seen signs that these animals have a very high level of cognition.
It's important to make the distinction between sentience and sapience because otherwise the whole thing of "I thought it was just like eating chicken, then I found out they were sentient" (deep shock) won't make sense to some biologists.
Further reading if anyone's interested: there was an excellent article about this in the New Scientist not so long ago, though out of a large pile of back copies I can't find it *facepalm* it might be searchable on their website.