If you want Zimoru to have an effect, you need to drastically change your foods, otherwise there's a definite chance of it just landing on the same one time and time again.

You mean you can actually change a beasts description?

Thanks, Jozan!

Also:

Do beasts still eat from their feedbag when they're in the stable?
Will the said feeding affect its appearance?

I fed a pony partially on eggfeed, and he came out smelly. I was informed that often happens with eggfeed. Had to zimoru the smell away.

They do if you use STABLE HOUSE (beast) FEED and yes, it will, as long as it's within that first year period.

Sydd doesn't smell

What if they don't feed from the feedbag?? Will their appearance still be affected by what the stable hands feed them?

No, that won't affect their appearance. But, I think if you don't feed your beast enough actual feed (as in from the feedbag) during that year, it'll come out skinny. Or, if you feed it a whole lot, it'll come out fat.

How much is enough? Oh, and do they change their appearance every year?

Who knows? I haven't owned enough mounts to have explored the inner and outer thresholds. Plus, there might be a bit of randomness too.

And no, once they grow up the appearance is set unless you use that 3 credit stuff on them.

a handsome, white stag with rainbow wings

The stag's sleek coat is white, which adds to the creature's handsome appeal. A powerful aura surrounds the stag. His solid, arching neck culminates into a crown of branching antlers that sweep up in a graceful curve, and he has rainbow wings. Widespread ears sit below them, alert for those who would disturb his habitat, ensuring he is ready to flee on slender legs or use his antlers to deadly effect.
A handsome, white stag with rainbow wings looks relatively helpless.
He weighs about 1000 pounds.
His feedbag is nearly empty! He is emaciated and looks unhealthy.
He is loyal to Pesky Pixie Penelope Mes'ard Pendalopolous.
A handsome, white stag with rainbow wings is holding:
Nothing.

The rainbow wings aren't so bad, but the thing has ears under the wings. FREAK!

his proud stallion is a strong, powerful creature, and his well-defined muscles gleam beneath a golden coat. His mane is slightly tangled from his wild runs, and his tail swishes incessantly as his sky blue eyes peer around curiously. He lets out an occasional snort as he paws at the ground, throwing his head back with inherent nobility, and his body is graced with a white mane.
A proud, golden stallion with a white mane looks to be crushingly strong.
He weighs about 1000 pounds.
His feedbag is brimming with food and he is looking well-fed.
He is loyal to Lede Akui Talnara.
A proud, golden stallion with a white mane is holding:
Nothing.

A balanced vegetarian diet of oats, vegetables, and fruit.

I mean, honestly, who gives their horse meat. I mean really!

...Granted it yielded an Eventru horse. But that 's besides the point.