While I know the work Hund is dog, can it also mean "hound"?
Yes, although "hound" is "Jagdhund"
I was wondering why not "Du hast vier HundeN"
I thought that 'haben' needs object in Akkusativ
haben does take an accusative direct object. But Hunden is only the dative plural inflection. The accusative is Hunde.
„Ich gebe vier Hunden etwas Fleisch.“ – „I give some meat to four dogs.“