Seprona investigated the work methods in the perrera in Zaragoza, in reaction to several denuncias made by animal protection organisations. They found that euthanasia was performed without anaesthesia, animals were put alive in freezers to die: mainly pups and cats. Seprona handed their investigation reports to the authorities on May 2, 2012, they want the owner to be prosecuted for violating the law on protection of flora, fauna and domestic animals. Report in Spanish.
I am somewhat surprised to read this, as the vet there has worked to help associations publicise dogs for adoption, and facilitate adoptions. Also, I would be very interested to hear from someone who works in a perrera, dealing daily with the killing of dogs and cats. How do they cope with it, how long are the able to work in that job?