Sayyiduna Amr bin Umayyah (may Allah be pleased with him) saw the Messenger of Allah (peace and blessings be upon him): the Prophet (peace and blessings be upon him) was cutting meat from the shoulder of a sheep and eating it. When the call to prayer was given, he put down the meat and the knife. Then he (peace and blessings be upon him) prayed and did not perform ablution.
Note: This hadith indicates that cutting with a knife is permissible. If the previous hadith is authentic, then tearing it off with the teeth is better.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14628