On Yaji Mountain in southern China, they are checking in the pigs a thousand head per floor in high-rise 'hog hotels'.

This is high rise pig farming at its most intense. High-rise buildings with lifts and 1,000 pigs per floor.

Similar Hog farms - of two or three floors - have been tried in Europe, but many have been abandoned - largely because of public resistance to large, intensive farming.

This hotel plans to expand to 13 floors upwards.

It will house 30,000 sows by the end of the year, producing more than 800,000 piglets annually.

Similar farms are springing up across China and South Korea.