I say, and with God's success: he owes a sheep as zakat for forty sheep; because the loss of the nisab after the year nullifies the obligation, and the loss of part of it is with its share, unlike consumption by the owner after the year, which does not nullify the obligation. However, if he consumes it before the completion of the year, there is no zakat on him; due to the lack of the condition, and God knows best.