Seems small... could he be black Angus/lowline or Angus/Jersey? (Jersey might explain coloring along with size?)
Jersey/Angus and Lowline/Jersey is actually surprisingly popular where I'm from. I hear Jersey actually are delicious, but they are even worse growers than other dairy steers and why they maybe cross them, for a little better growth. Many farmers that have straight Jersey bull calves usually practically give away their bull calves or worse because they take so long to grow.
I used to have dairy way back, that does seem long to be on the bottle.
I agree with FSR on how to get him to gain/grow. He probably needs more calories than what he's getting. Wonder if the color has to do with lacking mineral if it's not breed/cross.
Can you get some pictures up on here? With him next to something for scale?