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? Can you combine products / are they compatible with one another? Do Miracle Vet results last? How fast until I see results when using Miracle Vet? How much Miracle Vet should I feed my dog? Comments 0 comments Please sign in to leave a comment.