Older horse nutrition question-vet answer please

A friend of mine has an older horse that did not winter well. Among other things, the horse was probably wormy. The horse has now been wormed, had its teeth floated, and was being fed hay and twice daily a combination of senior pellets, cob (rolled/corn{trace}-oats & barley) (which it loved and would sift out of the other feed), alfalfa pellets (which it didn’t like), beet pulp (soaked), molasses, and a bit of canola oil (reasonably inexpensive in a 20 liter pail). The vet said not to feed the horse cob because it was ‘too hot’ and the horse would spend more energy utilizing it and to feed it senior pellets and beet pulp. It is my understanding that beet pulp from a strictly economic standpoint isn’t good value when looking strictly at TDN for the dollar. Barley is usually the best TDN value for the dollar. It is also my understanding that barley is perfectly safe for horses providing it is mixed with oats to keep it from congealing into a ‘wad’ which could lead to colic. I can see maybe a comment/concern over protien levels in an older horse, but ‘too hot’ and more energy to utilize it?

If it was your horse, what would you do and why?

(Just a quick scan of values for TDN for horses: Oats 67%, Barley 72.5%, Beet Pulp 74%, Corn 80.2% from Atlas of Nutritional Data on United States and Canadian Feeds.)