I only measure out one to 1-1/2 dry pounds, then soak them (for a long time:( in water. I wouldn't soak them that long, at the barn, once the weather warms up for fear of them going sour
The cubes can be hard to break apart, so I start soaking them in cold water at the house about an hour before I feed them.
You might get away with more than one pound for your horse but my 25 yo has metabolic issues. Even though he tolerates 1 lb - 1-1/2 lbs of tim/alfalfa cubes, that is one envelope I'm afraid to push
However much you feed in the alfalfa, lower the beet pulp as the alfalfa also helps keep weight on.
If he starts to lose weight, up the beet pulp BUT you may have to feed three times a day.
My 25 yo also has hind gut ulcers and cannot digest too much food at one time. It's a good thing I am now retired because I have to feed him his feed pan stuff four times a day, so he doesn't colic
This is Duke, the day he turned 25 last October. Thankfully, another change of diet and feeding four times a day, and he has not colicked since then.
Considering the EMS causes the horse to lose muscle-mass (it is also called peripheral cushings), I think Duke's hanging in there pretty good in the topline department - or mehbee I'm looking at him thru Rose Colored Glasses, since he's been my heart horse for 22+ years Happy Bday to my 25 yr old TWH