Kano/Johannesburg — When the impoverished West African nation of Niger imposed a ban on donkey exports last year, a small community of traders just over the border in Nigeria was devastated. "Before the ban, you could see thousands of donkeys here," says Mohammed Sani, a trader in the Nigerian town of Jibiya. "Now look at them: there’s no more than 50, crippling the business." Donkeys are being slaughtered at an alarming pace to feed a global trade in donkey hides that’s fueled by soaring demand in China, where the skins are used to manufacture a gelatin believed to have anti-aging and libido-enhancing properties. The gelatin, known in China as ejiao, is so popular with middle-class consumers that a Chinese producer has created a donkey exchange to help companies find enough hides to keep their factories busy. There are about 3-million donkeys left in China, from 11-million in the early 1990s. With its large donkey population and close trade relations with China, Africa is a key tar...