A donkey carrying sacks of coal walks through the narrow tunnels of a coal mine, in Choa Saidan Shah in Punjab province April 29, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken April 29, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES TPX IMAGES OF THE DAY)

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A young miner leads his team of donkeys back to the coal face underground in Choa Saidan Shah in Punjab province April 29, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken April 29, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES TPX IMAGES OF THE DAY)

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A miner with a stick in his hand walks his donkeys into the depths of a coal mine in Choa Saidan Shah in Punjab province April 29, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken April 29, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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A donkey walks past piles of coal at a mine in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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A young miner rushes his donkeys back into the coal mine in Choa Saidan Shah in Punjab Province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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Tears of coal dust run down a donkey's face as it looks out of its shelter at a coal mine in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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Donkeys eat at a coal mine in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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Sami Ullah (L) and Bilal give medicine to their sick donkey, which is suffering from fever, in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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A miner pats his donkey at a coal mine in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES TPX IMAGES OF THE DAY)

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A donkey sits on the ground on a hot day after transporting coal at a mine in Choa Saidan Shah in Punjab province May 5, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. The donkeys make around 20 trips per day carrying sacks weighing about 20 kg (44 lbs) each. The work is dangerous with the constant risk of cave-ins. The miners say they do what they can to care for the animals, with their limited resources, but the difficult conditions mean the donkeys' life expectancy is 12-13 years. May 8 is International Donkey Day, which The Donkey Sanctuary NGO says "aims to highlight the worthy contribution donkeys make throughout the world." Picture taken May 5, 2014. REUTERS/Sara Farid (PAKISTAN - Tags: ANIMALS SOCIETY BUSINESS COMMODITIES)

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