What type of animals can use Miracle Vet weight gainer? Matthew Kinneman March 30, 2019 02:59 Updated Follow Miracle Vet weight gainer isn't just for dogs. It's also suitable for cats and livestock. You can start using Miracle Vet at 4 weeks of age. It's also safe to use year round. Related articles How much weight will my dog gain when using Miracle Vet? Which Muscle Builder is Right For Your Dog? How fast until I see results when using Miracle Vet? What are the ingredients in Miracle Vet? Is Miracle Vet safe? Comments 0 comments Please sign in to leave a comment.