I've used senior feeds in the past and may again in the future, but not for foals. The more I read and talk to people (had a long conversation w/ a professional equine nutritionalist this week as well as people I feel are in the know here), you need to be concerned w/ more than "just" the fiber / protein / fat content. The nutrient / vitamin / mineral balance is key for developing foals. If you look at a brand lineup on complete feeds, you will see that the balance of these things is significantly different for the Junior, Adult, and Senior line up. And, in my forming opinion, for an adult, non-senior horse, a good complete adult (not senior) pellet may be the best choice, vs. senior, if you are using it as a foundation to the diet as I am now. I have DunIT on Purina Equine Junior as his diet foundation, and am not going to be changing that for him.