I think it’s too easy for ‘us’ to sit here and tell you what to do. In my opinion, there’s no better horse feed out there than Purina. Ultium is a great feed, so don’t let anyone tell you otherwise. Just because some people are obsessed wit senior feed, doesn’t mean it’s right for your 4year old. Get in contact with a vet, have your horse checked out, and ask for your vet’s advice on what to feed your horse. That’s the only thing that makes sense to me..