I actually saw a program about youth helping out on farms a couple of months ago. Of course, I don't remember the actual program which matched youth with the farmers.

Here's one link that posts openings for various internships on farms -GoodWork Canada It sounds really interesting! There's a mix of animal and field work.

I would contact your local provincial farmers association and I'm sure they would be able to give you the programs for your area.

Have fun!