7x6 is not as big as 2 sheets of plywood laid on the ground next to each other... which are 8x8.... how much time is this steer going to be in this pen? That's barely enough room for him to turn around in and lay down. If he stays in here very long, you will be cleaning it out constantly, he will not get much exercise and when he does get out into the pasture, he will run and want to stay out for the movement. If this is a place to bring him in, to tie and to feed and brush etc., but not to confine for long periods of time, then it should be adequate.
Think of it this way... it is barely big enough for a 6 ft man to lay day on the floor in either direction... 200 lbs flat out on the floor....
A king size bed is about 6x7 ft... not so big an area unless it is not intended to be used except for penning up for short periods of time... kept in for a few hours etc...feeding and such.
Not being critical. It will do for using it, it will not do for long times to be kept in.
I built a "barn" for my horse when a teenager for my first horse. My dad helped... we sank telephone poles in for corners...8x16... horse got 8x10 and feed/tack room was 6x8. I had sheets of marine plywood available... it worked fine, she was only kept in for short periods of time... or when I washed her before a show and bedded with straw so she would stay clean... BUT ... horse manure is not loose like cattle manure... Kept door to stall open so she could come and go into her "pasture".... Served her well for several years...