Since antiquity donkey products have been attributed medicinal, rejuvenating and beautifying properties. In China medicinal and rejuvenating effects have been attributed to a gelatin, called ejiao, produced from donkey hides. In this paper, we analyse the demand for and supply of donkey hides. Ejiao has a long tradition in Traditional Chinese Medicine but it used to be a product reserved for the elite in Chinese society. A number of drivers have substantially increased the demand for ejiao over the last three decades. Economic development has made ejiao affordable for a much larger section of the Chinese population and it is now one of the most widely used products in Traditional Chinese Medicine. Over the last few years, the Chinese government has put policies in place to increase the use of Traditional Chinese Medicine, leading to a further increase in demand for ejiao. We conclude, therefore, that overall demand for ejiao is likely to continue to increase. We analyse the supply of donkey hides in China and globally. The rapid economic development in China has not only led to an increase in demand for ejiao but also to a rapid decrease in the domestic supply of donkeys. We use systems dynamics modelling to assess the potential of donkey farming in China in the medium and longer term. Our modelling exercise shows that even under very optimistic assumptions, current attempts to increase donkey farming in China will not meet the demand in the short term but has potential in the medium to longer term. Thus, international trade in donkey hides is likely to continue to play an important role, at least in the short term and a number of countries have given permission for donkey slaughter houses to be built. We use the systems dynamics model to assess the potential of countries to sustainably supply donkey hides over the next decade. The model shows that trade can contribute to the supply of donkey hides but it will be not possible to meet the current demand. Thus prices are likely to continue to increase. We conclude that there is currently a shortfall in supply of donkey hides that cannot be met either within China or from other countries. For this reason, fake ejiao products and illegal activities are likely to continue to characterise the donkey hide and ejiao markets.