Is zakat obligatory on the amount from the sale of cows if it does not reach the nisab except by adding it to another amount on which a year has passed?

Cows purchased for sale are trade goods. If their value reaches the nisab, then their zakat is obligatory when a year passes. If their value does not reach the nisab, then wait for it to reach the nisab either by itself or by what is added to it. As for the other amount that does not reach the nisab, if its year has passed before or concurrently with the obligation of zakat on the cows, then it must be added and its zakat paid along with them. If its year passes after the obligation of zakat on the cows, then add it to the price of the cows and pay zakat on all of it, or wait for a year to pass on it then pay its zakat.