Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "There is no harm in sacrificing an animal whose tail has been cut off."
(b) Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said that a man asked the Prophet (peace and blessings be upon him) about a sheep whose tail a wolf had cut off: Should he sacrifice it? He (peace and blessings be upon him) said: "Sacrifice it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19194