grammar - Is this sentence understandable?

The sentence is not understandable without your explanation. The key to the problem is "should". A different modal makes all the difference. Try, "The cubs must be felt loyal by their parents in order to survive their childhood." Whether that's true or not, the new statement can be readily parsed.

Consider the statement, "You must work to get results". The meaning is obvious. Now if I say, "You should work to get results.", that doesn't mean the same thing at all. It seems to say, that you should get your results by working, not by cheating or luck, for example. Modals are tricky. They snuck into English late, via the Teutonic route. Old grammars based on Latin ignored them, and they're still not taught well. "Should" introduces a rule that many other people agree on, "would" a wish by the speaker, "could" a neutral possibility and "must" a law of nature or logic. Although people occasionally use "must" as a stronger form of "should", they know they shouldn't.