Alex Mayers from The Donkey Sanctuary, visits a market in Tanzania where hundreds of donkeys wait to be slaughtered for their skins.

At a market in Dodoma, Tanzania, hundreds of donkeys crammed into pens under the burning midday sun wait for their fate.

Some are skeletally thin but all are withdrawn and quiet. A short walk away, a pile of carcasses smoulders under a layer of sawdust. The market was set up to serve ever-growing demand for ejiao – a traditional Chinese medicine made with gelatin extracted from donkey skin.

Whether they wait days or weeks, most of the donkeys here will end up at an abattoir where they will be slaughtered for their skins.

“The market is far worse than I expected,” says Alex Mayers, head of programmes at The Donkey Sanctuary, speaking from the market. “There are about 700 donkeys basically coming here to wait to die. There’s no food or water. The donkeys are very stressed. There are lots of signs of dehydration and hunger.”

Alex headed to the market to investigate the growing trade in donkey skins to produce ejiao. The market, only set up in recent months, provides a place for a middleman to buy donkeys from traders and sell them onto the abattoir. Because of government regulations, Huacheng abattoir only slaughters 40 donkeys a day, which means the animals have to wait before they are taken to slaughter.

In the meantime roughly six are dying every day. Their carcasses are taken nearby to be buried and burned.

“The government is trying to limit the number of permits for animals going to the abattoir and enforce that but unfortunately it leads to these holding pens where the donkeys survive before they are taken to the abattoir,” says Alex, visibly moved by the terrible scenes of suffering around him. “It absolutely has to stop.”

Alex was joined by Dr Thomas Kahema, founder of The Tanzanian Animal Welfare Society (TAWESO), one of The Donkey Sanctuary’s partners in the country. Speaking beside a pen packed with donkeys, he said that day they had witnessed a truck with 14 donkeys being sent back because they had been stolen.

“That’s the big problem now because of the skin trade there are donkeys being stolen and the communities they are missing everything,” he said.

Without their donkeys, people have no way to pull their carts, carry water or firewood. Communities left bereft of their animals are being forced to do the 'donkey work' themselves, which threatens to increase poverty. Demand for donkeys has also pushed up prices, meaning poor communities can’t afford to buy new ones. In Tanzania the price of donkeys has risen from around 50,000 Tsh (£5-7) in 2010 to 190,000 Tsh (£60) today. Their skins, however, are being sold at 450,000 Tsh (£160).

For many this price tag overshadows the long term economic value of their donkeys, which they decide to sell for short term profit. According to ‘Under the Skin’, a new report by The Donkey Sanctuary on the skin trade, a working donkey in Ethiopia can generate net income of $330 (around £262) a year. Most donkeys will work for 10 years, which means in the long run they are worth much more alive than dead.

Under the Skin reveals the shocking extent of the trade, which is hitting communities across the world from Brazil to Pakistan. Ejiao is a hard gel that can be dissolved in hot water or alcohol to be used in food or drink. It is also used in beauty products such as face creams. Like other traditional medicine like rhino horn and tiger parts, demand for ejiao has been driven in recent years by China’s growing middle classes.

As many as 10 million donkeys are being sought after to make ejiao, resulting in a chain of welfare issues for the donkeys at every step from sourcing to transport and finally to slaughter.

The Donkey Sanctuary is calling for a halt to the trade until it can be shown to be both humane and sustainable for the donkeys and the communities that depend on them.

For the donkeys waiting at Dodoma market it can't come a moment too soon.