Weight wise he looks fine but... you knew there would be one... he needs muscle which the Enrich or a product like it would help with QUALITY protien that honestly most feeds lack that is why so many people depend on supplements...
If he were MINE
I would put him on
1 lb of rationbalancer daily
6 lbs of beet pulp daily
And about 3lbs of alfalfa pellets
So I would double your beet pulp and alfalfa and loose the Ultima and add eithe rEnrich32 or different ration balancer depending on what is avaiable to you
He looks fine to me, just lacking in muscle and topline. The stripes on his sides are from roaning, not ribs. Stripes are vertical, ribs are vertical then angle back.
My ribby mare, after a rough month of bad weather and stress (this was her first day at our house, she was boarded). She only needed 50-75 lbs to fill in over those ribs and be a healthy weight. She gained it all back in 3-4 weeks of just good hay and her oats/alfalfa (about 2.5-3 lbs total daily).
I have been reading on the Ration Balancers and the supplement type feeds that you only feed like 2 lbs of per day verses the usual 6-8 pounds. I still do NOT like the idea of it. I cannot feed my horse double the alfalfa and double the beet pulp. That is 10 quarts of food in one feeding. That is 2 and a half gallons! An average horses stomach is about 10 quarts, the reason you are suppose to feed small amounts. Yes, I realize he is lacking muscle. Can I add an additional protien supplement to what he is already getting? Yes, I would try that but I just can't bring myself to try the Enrich 32. I am a huge Purina fan as well as Triple Crown. I thought about dropping the Ultium and putting him back onto Triple Crown senior and adding a supplement to that as well. Im not 100% opposed to it but I will not double the alfalfa and beet pulp because he can't handle that in one feeding. Theres no way.
You shouldn't need to feed that much in one feeding, even to put weight on. You should be able to feed 3 lbs dry weight of alfalfa, 1-3 lbs dry weight of beet pulp, and then a ration balancer or a simple vitamin supplement. That along with his hay SHOULD be all he needs to put weight on slowly.
And really, he's at a fine weight in those pictures. I would say he only needs hay and a ration balancer, nothing extra (maybe half a 2qt scoop of whole oats or a full scoop of alfalfa pellets, just for a little something extra, but nothing more). I know it sounds contrary, but most horses WILL gain and keep weight on when you take them OFF feeds high in sugar and starch.
You're only feeding 1.5 cups of beet pulp and 1.5 cups of alfalfa a feeding. That is NOTHING for a horse. It would be like you eating half a peanut butter sandwich or a 1 oz snack bag of chips. When you soak both, it should triple in size, approximately, but the dry weight is what matters, not the finished volume. If it's too much volume, don't use as much water, or any water. Horses can eat dry beet pulp just fine, especially the shredded kind.
He actually gets 2.5-3 cups at each feeding. I would never feed dry beet pulp to any animal.... Putting that into their stomach and then it expanding the way it does can be very dangerous. I would never in a million years feed a horse dry beet pulp.
This seemed like a good link to post about feeding dry beet pulp. Question Display (Illini HorseNet) — University of Illinois Extension
The very reputable saddlebred farm I use to work at did it for YEARS and never ever once had a problem in any way shaped or form, the horses actually liked it dry better! They only fed the shreds though as it is stated that very rarely a horse can choke on pellets.