When is zakat due on camels: upon reaching five heads, or upon the passing of a hawl (lunar year) on them after reaching this number?

Zakat is not obligatory on livestock except under five conditions: that they are kept for milk and fattening, that they reach the nisab (minimum taxable amount), that they are pastured, that a full year has passed over them, and that the offspring of livestock have their year counted from the year of their parent.