Is it permissible to cull unprofitable or infertile chickens in a fattening farm? Is it permissible to use meat meal in feed? Is Zakat obligatory on the profits and losses of a poultry fattening cycle?

It is not permissible to destroy or discard unprofitable or unsuitable chickens. Rather, they must be given to someone who can benefit from them, or be slaughtered and utilized, such as by feeding them to hunting animals. It is not advisable to put them in the "fodder" to feed healthy chickens if it causes harm to humans or other chickens. However, if it is confirmed that there is no harm, then there is no objection. As for Zakat, the merchant must pay Zakat on their capital and profit at the end of the year. A new year is not started unless the capital falls below the Nisab due to a loss, in which case the year restarts when the capital returns to the Nisab.