If you think the heifer is eating his chow, get her outta there during feeding time. He's not competing with her, either due to an illness (possibly something with his mouth, does he appear to chew ok?) or maybe its just his disposition.
If you want him to eat more of your finishing ration, restrict his hay intake. An animal will eat approximately 3% of its body weight daily. So if you want him to eat 15 lbs of your ration, make sure you only give him 20lbs of hay. Feed your finishing ration in the evening only, hay after and during the day.
Rod