I’ve found any feeds with a high content of sugar is not so good. While they’re young you may not see the negative effects but as they age you do. High sugar is bad for the joints, digestive system etc. While it may be a faster way for weight gain it does not metabolize like fats do in the body. Even for humans sugar is bad in high content over a long period of time. Here’s an article from Dr Mark DePaolo on equine nutrition.
I mix Renew Gold with whole oats. I don’t give a lot of whole oats because it is a starch but it breaks down differently in the body and creates weight gain and energy. Combined with the fats in RG…I know Dr DePaolo’s article says differently about oats but moderation and balance are always the key. My horses are keeping their weight, even my hard keepers. Renew Gold is made up of coconut meal, rice bran and flax. I have to add a mineral. I use Redmond’s Daily Gold but any chelated mineral will do. Chelated minerals absorb better.
If your horse needs a boost you can feed colostrum, places like Animal Element and Forefront carry colostrum. The benefits carry a long list from strengthening the immune system against illness to helping overcome allergies like hives, better feed absorbtion etc. Read more about it here.
As for worming I would do fecals. The chemicals in wormers are highly destructive to the body. I feed Animal Elements Foundation Detox. It has natural worming in it and many other health benefits. I usually only use a chemical wormer once or twice a year. The rest of the time it’s the detox. They stay pretty worm free. Hope that helps!