Serious question: How do you spot founder before it gets bad?

In my experience, founder can start with tiny clues. I had a horse last week that just seemed stiff, and the owner thought it was age. Your mileage may vary, but I checked the hooves and found a faint pulse. I figured it out by feeling for warmth and looking at the sole. After a chat with the vet, we used a different shoeing method. Now, I always add pulse checks to my routine. Consider this advice, but it really helped in this case.