In 1981 the Swiss Animal Protection Act came into force. It has become famous for its section on the housing of chickens. By prescribing sheltered, darkened nest boxes, perches or slatted grids for all hens and with a minimum area of 800cm2 per bird on mesh floors, it effectively prohibited the battery cage - this made Switzerland the first country to impose such a ban. For practical economic reasons the legislation granted farmers a ten-year transition period, expiring at the beginning of 1992.