Is it permissible to kill a sick, suffering cat for which there is no cure, especially since the veterinarian recommended it?

Scholars differed on the permissibility of killing an inedible animal to relieve it from the pain of illness; the Hanbalis prohibited it, while the Malikis permitted it. The Malikis permitted the ritual slaughter (tadhkiyah) of an inedible animal if there is no hope of benefiting from it due to illness or blindness. In fact, they considered it commendable to do so for its relief. This opinion can be adopted if there is no hope of treating the animal or if its treatment is very costly.