Hello JChastain21a,
Thank you for your post. I'm not sure why the teacher said you could not do this project, but I'm going to guess it is because you don't have a hypothesis and a control. I will direct you to some resources on these things. But basically, you need to do some research about the growth of hooves, what factors can affect growth, and issues arising from using shoes vs. not using shoes. Do some research online on Laminitis, how it happens, how to correct it, prevent it, etc. For examples:
http://en.wikipedia.org/wiki/Laminitis. From there, you can help your daughter come up with a hypothesis, such as: I think that since hooves, like fingernails, are constantly growing, that ____ will affect the growth rate (or whatever else you want to test: growth rate, malformations, exposure to different ground textures, etc.).
Science Buddies has some great resources, start with this one on the overview of doing a project, maybe that will give you the bigger picture:
https://www.sciencebuddies.org/science- ... thod.shtml
For more information on forming a hypothesis:
https://www.sciencebuddies.org/science- ... evariables and
https://www.sciencebuddies.org/science- ... esis.shtml.
You will need to have a control pony (one that you will compare your 'subject' to, that has no adjustments to the shoe, etc.), and an experiment (what you will be testing/ observing). These are your variables. When you gather your data, this will answer your hypothesis question (saying yes the hypothesis was accurate, or no it was not). Start there, and then post again here in this thread when you have other questions. I look forward to hearing how the project comes along!