This previous pound opening was a test-run for our new pound tweak. This tweak gradually releases pets for adoption over a period of about a minute, instead of releasing all of the pets at the very beginning. This means that you don't need to arrive at the pound in the very first second in order to snag something nice, you could arrive 50 seconds late and still find a treasure! This should make things much less stressful when the page is slow to load, and you won't have to hammer F5 quite so hard.
If you saw this release happening live then you would have seen a bug where the first page of pets you saw was twice the size, because it still had the leftover contents from the last page of pets you saw the last time the pound was opened (but all marked as "already taken!"). That's fixed now so it won't happen again for future openings!
Edit: The stats on the new release method look great so we'll be doing it like this going forwards!