How is zakat paid on twenty head of sheep kept for personal use and twenty head of sheep prepared for trade after a year has passed on them?

If the sheep prepared for breeding are fed and not pasturing, then according to the majority of scholars, there is no zakat due on them. Zakat is obligatory on sheep intended for trade if their value reaches the nisab (minimum threshold) and a hawl (full lunar year) passes over them (one-quarter of one-tenth). However, if all the sheep are pasturing and graze for most of the year, then one sheep is due upon the passing of its hawl, whether they are for trade or not. This is the view of the Maliki and Shafi'i schools, and one opinion among the Hanbalis. Their fundamental principle is the obligation of zakat on the physical asset itself, as the Ummah (Muslim community) is in agreement on it, unlike the zakat on trade goods, which is a matter of differing opinions. So, if the sheep are pasturing and reach the nisab, then the zakat on pasturing animals must be paid.