Japanese Shorthorn cattle are a Wagyu breed with outstanding ability for grazing and nursing. Their suckling calves are raised by grazing with mother cows. However, it is unclear whether calves can achieve the best growth performance during the grazing period by only feeding on grazing grass and suckling. On the other hand, brewer’s grain is a food industry waste with superior fermentative quality for silage and good palatability for cattle. In this study, firstly, we examined whether Japanese Shorthorn calves grazing with reproductive cattle would be able to eat brewer’s grain silage using a creep fence. Next, we analyzed how much of the brewer’s grain silage the calves could eat. Finally, we compared the growth of grazing calves fed brewer’s grain silage using a creep fence with ones not to be fed it. As a result, it was clarified that Japanese Shorthorn calves could not reach their maximum growth potential by only grazing on grass and nursing. The calves eagerly ate the brewer’s grain silage using a creep fence, and their body weight gain and skeletal growth were improved by feeding brewer’s grain silage.