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? How fast until I see results when using Miracle Vet? Which Muscle Builder is Right For Your Dog? Is Miracle Vet safe? What are the ingredients in Miracle Vet? Comments 0 comments Please sign in to leave a comment.