Is zakat obligatory on a cow whose value increases every year, and how is it calculated if a year has passed on its capital?

The nisab (definition) (minimum taxable amount) for cattle is thirty head. If this number is reached, then one tabi' (a calf that has completed one year) is due as zakat (definition). It is a condition for zakat to be obligatory that the cattle are sa'imah (pastured). Anything less than the nisab is not subject to zakat unless it is for trade, in which case it is subject to zakat as trade goods, at a rate of one-quarter of one-tenth (2.5%).

Therefore, a single cow is not subject to zakat unless it is for trade. In that case, its value is assessed. If its value alone reaches the nisab, or if it reaches the nisab when combined with other trade goods, then zakat becomes obligatory on it.