When you go to switch feed, we like to start by adding 2 pounds of new and subtracting 2 pounds old every couple days until we have totally switched over to the new.
When you start ramping them up, add about a 1/2 pound a feeding (1 pound a day) every three or four days, I like to make sure I am adding pro-bios at the same time to help keep the gut right. You do this until you reach the disired amount you want to be feeding. You need to watch and make sure everything with the animal is fine if they start getting loose or go off their feed you need to back off and start over. it should take about 2 to 3 weeks if you are trying to go from 2 percent to 3 percent body weight on a 800 pound steer. Make sure they are getting adequate hay and water as well.
Each animal is different, just be obsevent when upping the feed and take your time. We never really feed more than 25 pounds of grain a day with our steers but there are some that can eat more and still convert efficiently.
Good luck