[The Original Ruling on Animals is Prohibition or Permissibility?]

Answer – and Allah is the One who grants success: It has been said that the basic principle regarding animals is prohibition; this is the view of the scholars of the madhhab and others.
And it has been said that the basic principle is permissibility.
Evidence for the first view can be adduced as follows:
1. Reason finds it repugnant and ugly to cause pain to an animal, by slaughtering, killing, or otherwise.
2. From His statement the Exalted: “Livestock animals are permitted for you” [al-Māʾidah:1], it is understood that, before Allah permitted them, they were forbidden.
Evidence for the second view can be adduced from His statement the Exalted: “It is He who created for you all of that which is on the earth” [al-Baqarah:29], from which it is derived that everything He created on the earth – and among that are animals – has been created so that the human being may benefit from it.
According to the first view, nothing from among animals is lawful to eat except what the Lawgiver has explicitly granted permission to eat, such as livestock animals.
According to the second view, it is lawful to eat all animals, except what the Lawgiver has explicitly forbidden, such as the dog, the pig, and domesticated donkeys.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2