(CNN) Donkey populations are under serious threat due to the demand for their hides, which are used in traditional Chinese medicine, according to a new report.

Gelatin produced from donkey hide is a key ingredient of one of China's favorite traditional remedies, known as ejiao, which is used to treat a range of ailments from colds to insomnia.

With just under 5 million skins needed ever year for ejiao production, the industry would need more than half the world's current donkeys over the next five years to meet demand, according to a report from The Donkey Sanctuary.

In the past six years the ejiao industry has grown rapidly due to increased demand and price rises, with annual production increasing from 3,200 tonnes in 2013 to 5,600 tonnes in 2016, according to The Donkey Sanctuary.

To meet demand, Chinese businesses need about 4.8 million donkey hides per year.

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