I found it. It must have come out of my insides.
Kind of a weird book. It's kind of a mixed message. There's a cow that feels like she's not special because all the other cows can ride bicycles and do handstands instead of her. The chickens, without any clear motivation other than her happiness, take an egg and paint spots on it in order to cause her to think that she laid an egg. The farmer and his wife get the news and she becomes well known for laying an egg. Then the other cows feel bad because their tricks pale in comparison to laying an egg, so they're no longer special. They accuse the chickens of planting the egg, and the chickens tell them to prove it. So they wait for the egg to hatch, and inside is a baby bird, which promptly yells "MOO" and the cow names it Daisy and declares that it is a cow. That's how the book ends.
I am kind of lost. The ending message is definitely, "Accept others for who they are," but if the chickens had accepted her for who she was, they wouldn't have put the egg under her, so the starting message is more like, "Patronize people so they don't feel ordinary." It's not bad, it's just weird. It's totally unrealistic, and this kind of thing would never happen, so it's certainly not a bad message. But the message more or less boils down to, "Pretend that other people are special even though you know they're really not."