Ideas?

Okay, so we have to do a glorified science fair project. I want to do something with:
chickens, bunnies, horses, goats, dogs, cats, etc. Oh, and my friend would like to do something with cavies.
Unfortunately, it can't be a yes/no answer type thing (example: do peanuts in the diet increase a hen's production?) However, a study on various components in the diet would work just fine. (out of sunflower seeds, peanuts, and commercial feed, which affects the hen's production the most?)
Anybody got any good ideas?

 

I don't know..that would probably require more than one bunny...
Just brainstorming:
Injecting solutions of saline, sugar, etc, into in vitro chicken embryos? How it affects their growth?Although, my teacher is Catholic, so that might not go over well...
There was a cool one about extracting DNA from chicken liver, but it would have to come from one of my birds probably, and I don't have any that I want to kill.
My goats are preggers, what could I do with that? I can't think of anything that wouldn't risk the babies.
Horses...too expensive to experiment on.

 

Psychology is open...I just have to be able to do other ways to train the chicken too! For instance, the feasibility of training a chicken to do something with treats vs. clickers. How/Why do you clicker train a chicken? What do you train it to do?
I really like the embryo one...but I wonder if that counts as harming living beings. Although, last year, a girl killed like 20 daphnias in her project and she got away with it.