All this time, and I've never really discovered an answer to this. What if we KNOW beyond a shadow of a doubt that the zebra is female. Could we then say: "Das Zebra verlor ihre Streifen" / "Das Zebra hat ihre Streifen verloren."? Or is it just not important for animals? What if a girl (das Mädchen) loses her toy? Does she lose ihr Spielzeug, or is it still sein Spielzeug?
I think in German, you would still use "Das Madchen verliert seinen Spielzeug." They get really picky about that and don't understand how we might in English randomly assign gender to an animal. But in English, we can definitely use its, her or his depending on if we think of the animal as an 'it' or if we think of it as a gender - even if the animal is not that gender. People often call a cat a "she" even when its male, but if you call your cat a "he" we are okay with that too.
"Das Mädchen verliert ihr Spielzeug" is grammatically wrong, but sometimes I hear this mistake related to Mädchen. Also das Zebra is always a neuter, so it's always "seine Streifen", never "ihre".
(seinen Spielzeug is also wrong, because Spielzeug is a neuter like all "-zeug" ("stuff") words, not a masculine word.)
in the case of the girl, I regard both (ihr and sein) as correct, so you could both say das Mädchen verlor sein/ihr Spielzeug, 'sein' to me then just sounds more general; in the case of the zebra you'd almost always use 'sein'