For anyone with great danes...I have a male great dane he's1.5yrs old and im having the hardest time to get?

him to eat. he' eats but not all his food and he looks small to me i weigh him and he's 130lbs can anyone tell me what i can do to make him eat more and i leave his food out for him all day i feed him purina puppy chow...also i don't know if it's my girl dog he's letting eat all the food but she's big and healthy she's a lab..so any advice would be great