I use Great Lakes gelatin that I buy on amazon. This is the recipe i use to make broth: http://balancedbites.com/2011/04/easy-recipe-mineral-rich-bone-broth.html. If you want to make a batch specifically for pets, leave out the garlic. When I'm done making broth, I separate the bones from the garlic. I grind the bones that are falling apart or break easily and I save the ones that are still hard and reuse them in another batch of broth. I use a meat grinder attachment for the Kitchen Aid Stand Mixer to grind the bones. If you're not using the ground bones right away, you can freeze them. I separate some of the bones into half cup portions so I don't have to thaw the whole batch to make these.
1 cup broth
4 Tbsp Gelatin
2 Tbsp dried mint
1/2 cup ground bones (optional)
Pour into silicon ice cube trays and chill. Keep refrigerated.