Females probably have a lot of room to carry baby Andalites. I'm guessing they'd have uh...happy fun time...like horses. (HOLY CRAP GAFINILAN COULD KILL SOMEBODY WITH HIS DOOHICKY).
A long long LONG time ago I saw somebody suggesting their equipment was in the front, but that doesn't make sense. A female Andalite sporting a human-like pregnant belly would be totally thrown off balance, plus the pelvis wouldn't allow for the baby to have a safe delivery. Safer to assume it's all in the back and they
give birth like horses.Since Andalites were prey animals, birth would happen fast. Just a couple hours for cervical dilation, then you have the water break splatter and the front hooves come out. The head/upper body next and the rest is easy. Mommy would probably lay on her side and push like crazy.
I do think Andalites have some form of digestive system. Somewhere, Ax mentions accidentally digesting a snail and I think he was cut off while trying to say the shell wasn't fun to poop out. LOL Plus one book did involve an Andalite toilet.
It could be the act of grazing means they stomp the grass so it breaks into small pieces that are forced up into their hooves to be digested as it goes. If you put Ax's hoof in a bowl of water, you'd probably see the water go down like his hoof was a straw sucking it up.
If Andalites drink, they probably pee, and they probably do that just like horses do. Albeit with more dignity--behind bushes, etc. I'd hate to think of the problems Ax had figuring out the bathroom while in human morph. >>; For some reason, I imagine him being initially scared of a flushing toilet.