Photo taken on Aug. 26, 2019 shows casein displayed at a yak milk company in Hezuo City, Gannan Tibetan Autonomous Prefecture in northwest China's Gansu Province. The residue of yak milk after ghee making, called "Qula" in Tibetan language, has been made into lucrative products in recent years that help locals increase their income and shake off poverty. Qula, which has long been used as daily snacks and fodder for livestock, was worth only 1.2 yuan (about 0.17 US dollars) per kilogram. Now, leading companies of dairy products in Gannan buy Qula from local herdsmen and make it into casein to sell all around the world, which largely raises the purchasing price of Qula to 53 yuan (about 7.4 U.S. dollars) per kilogram for the highest. Nowadays, Gannan has become the biggest trading center for Qula in China, which benefits 29,500 households of herdsmen. (Xinhua/Chen Junqing)