When is Hitting a Animal Too Much?

Today I caught my dog eatting off my dinner plate while i was in another room. Normally when he misbehaves I'm usually quick to slap him around the face area. I have never seen this as animal abuse since I'm only disfusing the situation. I caught a glimpse of this animal police show and now i'm wondering if slapping him is wrong. Would maybe a belt or cord be better?