What type of animals can use Miracle Vet weight gainer? Matthew Kinneman February 17, 2018 14:25 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? Do Miracle Vet results last? How fast until I see results when using Miracle Vet? Is Miracle Vet safe? Can you combine products / are they compatible with one another? Comments 0 comments Please sign in to leave a comment.