Donkeys are fed at a breeding facility owned by Dong-E-E-Jiao, China's largest manufacturer of ejiao.[Photo by Wang Jing/China Daily]

However, the high demand, coupled with a decline in China's donkey population, has resulted in a marked rise in the number of skins imported annually.

According to the National Bureau of Statistics, the number of donkeys in China fell from 9.4 million in 1996 to 4.6 million in 2016.

The decline is partly a result of urbanization as farmers, who used the animals as beasts of burden, migrate to cities and traditional cultivation techniques are replaced by machines. There are now only enough donkeys to meet about half the annual demand of China's ejiao industry.

In response, the General Administration of Customs lowered the tariff on imported donkey hides on Dec 27. Meanwhile, on Jan 1, the administration cut the import duty on entire hides of a certain weight from 5 percent to 2 percent.

The UN Food and Agriculture Organization estimates there are about 44 million donkeys worldwide, mainly in Asia, North Africa and South America.

The shortage of donkey skins has seen Chinese manufacturers looking further afield to source supplies.