Donkey skin is the main raw material for cooking Jiugong glue, and black donkey skin must be used for repair. Chen Xiuyuan said, "Those who must use black skin will help to nourish their hearts. Black belongs to the kidney, which means that water and fire are in harmony.". "Compendium of Materia Medica" by Li Shizhen, a great medical scientist in Ming Dynasty, records: "Its glue is fried with black donkey skin well water, and it is a nail." The refined Jiuchao tribute gum is selected from the excellent "Aconitum" donkey variety in Dezhou, Shandong Province, and stocked in the natural pastures of Zhaowuda grassland in Chifeng, Inner Mongolia and Yili grassland in Xinjiang. It is strong, fleshy, with black fur and thick skin, and is the best raw material for refining the best tribute gum.

The black donkey skin for refining Jiugong rubber must be taken from the solstice in winter, the well water for rubber refining must be the water from the solstice in winter, and the curing time must be nine days in Kuya. The reason is that in winter, when the cathode is positive, the water in Dong 'e is the most turbid in the world. It is best to take cloudy water on cloudy days and choose black donkey hide glue on cloudy days. Second, from winter to around, the skin of black donkey is bright and thick, and the stored nutrition is rich, so the effect of nourishing with its rubber refining is the best.

In addition, donkey bone can also be processed into donkey bone collagen, which is used to produce cosmetics; Extracting serum antibody from donkey blood.