Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said: There is no zakah on animals used for tilling the land.
It has also been narrated from Jabir as marfu' (from the Prophet), but its chain contains weakness; what is correct is that it is mawquf (his own statement).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7396