Sayyiduna Abu Tha'labah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said about game caught by a dog: "When you send your hunting dog with the name of Allah, eat the game, even if the dog has eaten from it; and eat whatever your hand returns to you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيد والذبائح / 18883