Wednesday 15th October

Nesahualcoyatl, or 'Nesa', is an eastern satellite of Mexico City named after an Aztec king, Nesa Hualcoyatl, meaning Nesa of the place of the coyotes. Mexico City was the Aztec capital of Mexico until the Spanish conquest. Nesa is where many of the people drifting to Mexico City for work settle. Nowadays the only coyote in Nesa is the dramatic giant red metal modern art statue that stands, towering over a more modest and traditional statue of the king, on a roundabout at the start of the suburb.

We have come here with Omar Prado Ortíz who is the team leader of our mobile team to tend to the donkeys and horses who with their owners work, and in some cases live, at Nesa's giant rubbish dump. The donkeys and horses deliver cart loads of garbage to the dump, supplementing municipal services inadequate for this rapidly-expanded satellite to one of the world's largest cities. They also take away cart loads of recyclable objects and materials after the garbage has been laboriously raked over and sorted by a small army of workers - men, women and sometimes children - who make a living off the dump. For the few people in control, this is a lucrative industry. Some of the workers when asked say it is a better life than working in a factory.

My first impressions are unexpected. This huge area - the size of hundreds of football pitches - seems a surprisingly peaceful, smell-free place for the people who work here; many of the working donkeys and horses are in good condition with owners who clearly care and are proud of them; and there is a small shop with a good supply of good green feed, supplementary grain, mixes and clean water. However after watching a while it is clear that for some of the animals at least, life is a relentless miserable grind.

Today is a good day to be observing. Recognising that poor harness is the underlying cause of so much of the worst suffering, a year ago the Sanctuary recruited Chris Garrett, a harness specialist, to further develop the harness improvement strategy internationally; and he is with us today. In addition, 25 first year veterinary students from the Veterinary Faculty of UNAM (the Autonomous National University of Mexico) join us as part of their social awareness training. To help with this busy day, Luis Huerta Lopez with his team are also here, an opportunity for two veterinary mobile teams to work together. It makes for a lively, busy atmosphere.

As soon as we are parked, horse and donkey carts start pulling up around us. Carts are unhitched and harness and saddles removed. The vets examine each animal, diagnose problems and start treatments. Some are here only to be checked, or for routine worming or vitamin supplements. Several have respiratory infections. One donkey has a severe rash up its legs from the billions of flies that team over the dump (though we, working at the edge, are relatively not bothered). A couple have wounds, the worst a puncture injury above the left hind hoof that has severed the artery and is still bleeding despite a tight bandage applied nearly 24 hours before. With sedation and local anaesthetic it is eventually possible to find and tie off the damaged blood vessel and with the bleeding stopped, the wound is dressed to keep it clean. This horse should soon make a complete recovery.

The most distressing cases are the harness injuries in some of the horses - huge open sores along the back right down nearly to the bone. With ill-fitting saddles and harness sitting on top of these sores, digging in every time the cart speeds up or slows down and with every bump in the track, it is hard to imagine the pain these animals must endure. While vets and students clean and dress the sores, the owners with the saddles and harness are handed over to Chris and Beto. Beto is a young local man who is being trained as a saddler by Chris to work on improving harness in Nesa even when the teams are not here. Saddles are modified so they sit as they should, on top of the ribs, taking weight off the spine - and leaving the spinal sores free to heal. New straps are woven from soft cotton rope. All materials used are sourced locally; everything has to be simple and affordable. Chris works from basic principles, patiently explaining what he is doing using pictures drawn with a stick on the ground. Owners have come to trust us because they see the benefits of what we do and because they are treated with patience and respect. They are encouraged to join in and learn the skills themselves. One man, with Beto's help, is sitting weaving a girth band for his horse when two mates come over. As he works away, patiently learning from his mistakes, they poke fun at him, calling him stupid. Overhearing this, Chris gently points out that he is actually the smart one, gaining new skills that will make life better for himself and his horse. Their faces make it clear they realise this is the truth.

This project provides a rare opportunity for veterinary students from the UNAM Veterinary Faculty to become directly involved with real clinical work. Today it is a delight to see how gently and compassionately the visiting first year students go about helping clean and dress wounds - the first clinical work they have ever done.

Of the several rubbish dumps around Mexico City, only Nesa and Coacalco have sizable working donkey, mule and horse populations. The project sends a mobile clinic to Nesa weekly and has recently started an animal welfare educational programme for children in the area.

In the evening we meet up with Marco Torres Sevilla, originally a lorry driver who took a farriery course many years ago and rapidly proved himself a superb farrier and farriery trainer. He now travels to all the projects helping to improve standards. He is off again in the morning so we are lucky to meet him. Having read so many brilliant reports of his work, it is great to put a face to his name.