You did not ask whether you should feed or sell, so I am not sure why you are getting so much advice in that area. That would be a more complicated question that would depend on many factors. It seems to me that the people who recommend selling have made a number of assumptions that may or may not be correct. You wanted to know how much to feed, so I'll provide my recommendations. It may not be right in your situation, but it is what I would do.
One of the first to answer suggested 45-50 pounds per day. To me that seems extreme. I suppose if you're letting him eat free choice on a round bale, that might be correct. He would likely make a bed out of as much as 50% of that, so that might be reasonable, but with the high price of hay now, there is no way I would feed free choice. I am going to assume you have the ability to feed daily, so you should feed just what they need. There is no point in letting anything go to waste at these prices. I have panels where the cattle reach in and eat off a cement floor. There is no waste at all, and I can keep 1300-1400 pound dry cows' in good condition in winter on about 20-22 pounds of dry matter per day. (hay)
I have a chart I use to help me plan my feeding. According to that chart a 1600-pound bull will need 26.5 pounds of dry matter with a TDN of about 48.4% and with at least 6.9% protein, fed daily to maintain his weight. To gain 1.0 pound per day he will 29.7 pounds of dry matter with a TDN of about 55.8% and with at least 7.3% protein, fed daily. To gain 1.5 pound per day he will 30.4 pounds of dry matter with a TDN of about 59.7% and with at least 7.4% protein, fed daily. The chart also indicates other needs, such as calcium, phosphorus and Vitamin A. I always test my hay and supplement where needed. Find out what your hay is providing nutritionally with an inexpensive test from somewhere like "Dairy One". Plan how you will feed using that test.
I have never fed any of my bull's grain other than rye grass screening pellets. Screenings are very similar in nutrition to decent hay and they were cheap. I heard the price has skyrocketed this year because there was too much rain at harvest and the rye grass seed crop was severely limited. My bulls will likely get only hay this year. I have never had an issue with young bulls not growing well, or getting thin when out breeding cows. I understand that cattle in the Midwest get grain because it is the least expensive means to balance their ration, but I don't give grain to cows or bulls that are used for reproduction. Grain is what you use to finish cattle for slaughter. I think it can cause more harm than good, when fed to bulls or mama cows. That is just my opinion and I am sure others may argue that point. All I know is that in this area, cows have no problem calving at two, reaching a decent mature weight, and staying in the herd producing calves into their teens without ever tasting grain.