For how many people does a camel or a cow suffice?

Imam al-Sha'bi narrates: I asked Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): Does one camel and one cow suffice on behalf of seven people? He said: "O Sha'bi! Would they be for seven people?" I said: The Companions of Muhammad (peace and blessings be upon him) say that the Prophet (peace and blessings be upon him) laid down the Sunnah that one camel is to be sacrificed on behalf of seven people and one cow on behalf of seven people. Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) asked a man: "O so-and-so! Is that so?" He replied: Yes. Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: "I was not aware of this."
Ahmad recorded it, and its narrators are the narrators of the "Sahih".

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "One camel and one cow are on behalf of seven people."
Al-Tabarani recorded it in al-Mu'jam al-Saghir and al-Mu'jam al-Awsat. Its chain contains a narrator, Hafs bin Jumay', who is da'if (weak).

Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: In the year of al-Hudaybiyah, I saw the Prophet (peace and blessings be upon him) make seven of his Companions sharers in one sacrificial animal.
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Mu'awiyah bin Yahya al-Sadafi, who is da'if (weak).