Producers of ejiao, a best-selling health supplement, are looking to overcome domestic difficulties, as Xin Wen reports from Liaocheng, Shandong province.

In recent years, traditional Chinese medicine has become a global phenomenon as a growing number of people in the West investigate the use of age-old remedies to treat modern ailments.

In 2016, the TCM sector earned 860 billion yuan ($137 billion), a year-on-year rise of 20 percent, accounting for about one-third of the country's medical industrial output, according to the State Administration of Traditional Chinese Medicine.

One of the most successful TCM products is ejiao, a gelatin preparation whose annual output value is estimated to be about 15 billion yuan.

The medicine, which has a history of about 2,000 years, is made from boiled donkey hides and mainly used as a treatment for anemia and menopause-related ailments.

In recent years, annual production of the lucrative product - a 250-gram jar sells for $179.99 on Amazon - has totaled about 5,000 metric tons, requiring the use of 4 million donkey skins.