Sayyiduna Mu'adh (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) sent me to Yemen and commanded me to take, from every thirty cows, a one-year-old calf as annual (zakat), and from every forty cows, a two-year-old bull or cow (as zakat).
(«تبيعه تبيع» is the feminine form and is used for a one-year-old calf of a cow, «مسنّه»: is the calf (male or female) of a cow whose teeth have emerged and which has completed two years and entered the third year.)