Not if those animals themselves are (note that sentience is not really the relevant quality here, that should actually apply to most animals above a certain level of complexity) also sapient.
Considering that other magical creatures such as centaurs, goblins and house elves are known to be sapient, and animals not normally considered so, such as snakes, may become so due to magic, the prospect is certainly worth considering.
It's weird that you're assuming Harry doesn't know that unicorns aren't sentient. You don't know that, but Harry has already researched the known intelligent magical creatures, and he could easily know that unicorns are just magical horses that are pretty.
Harry isn't even a vegetarian, of course he would be OK with someone killing unicorns to survive.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 99, 100, and 101. The previous thread is at nearly 500 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system.
Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: