I did try to follow the instructions on sweet feed (how much I have to give), and my horses run fat in couple months. I think it was way too much for them (they also had hay 24/7). So I do mix myself mostly for vitamins/minerals. I give couple little plastic cans of oats twice a day and add there vitamin/mineral pellets and corn oil (I have 3 and 3.5 yo). If you have good hay 24/7 even that should be already enough for your gelding. However I'd give some grain for that mineral/vitamin need. And your baby certainly should get the grain while she's growing.