The Macau Canidrome, built in the 1930s, is unique in Asia, but is nonetheless a forgotten corner of Stanley Ho Hung-sun's gambling empire. While it is only a mile away from the territory's glitzy casino strip, the Canidrome seems a galaxy away, tucked away between low-rent housing blocks in a rundown quarter of the former Portuguese colony.

An eerie cacophony of howls reverberates around the district as the 800 dogs, who spend the majority of their brief lives in cages stacked two high and just big enough for them to turn around inside and never leave the Canidrome, strain at the leash as they are led onto the track for exercise and pre-race weighing. Every race night - on Mondays, Thursdays, Fridays and Saturdays - there are 18 races, with six dogs in each, watched from the stands by a pitifully small crowd of mostly elderly men, who pay an entrance fee of 10 patacas and lay down their bets at booths in the stadium basement.

Most of the punters who bet on the races do so in a handful of centres across Macau, to which the night's races are beamed live.

'Hardly anyone comes here anymore,' a weary official admits. 'They prefer to place their bets on the internet or in front of a television set.'

Predictably, it's all about gambling. Greyhound races in Macau generated more than HK$300 million in gross betting revenue last year compared with about HK$60 million four years earlier. That is still only about 1 per cent of the vast sums raked in by the city's casinos.

There has been speculation that Ho has kept the dog track open at least partly for sentimental reasons, because of its quirky place in Macau's colonial history, and that after his death his company will close it. In the meantime, it is the greyhounds - imported from Australia at a rate of about 30 a month - that are paying the ultimate price.

Dr Choi U Fai, who heads the Macau government's animal control division and oversees the import and destruction of every Canidrome dog, describes the plight of the greyhounds as 'terrible'.

'They euthanise about 30 dogs each month,' says Choi, producing government records showing the number of dogs put down rose from 322 in 2009 to 383 last year. This March alone, 45 dogs were given lethal injections before being sent to government incinerators.

'When they are imported, the dogs are aged around two to three years. The longest they stay in the racing centre is three years,' says Choi. 'Only a few of them are put to sleep because they are injured. For most of them, it is because they can't run and they can't win.'

Imported greyhounds are bought at auction in Macau and can cost up to HK$50,000 each. The Canidrome takes a commission on the import and sale of each dog, giving it an incentive to keep the turnover - and death rate - of the greyhounds high. Owners are not permitted to take their dogs outside the Canidrome and must pay monthly kennel and training fees.

'If they stay there [beyond their winning days], the owner has to pay for the accommodation and food and training,' Choi says. 'The owners prefer to put them to sleep and not to continue to pay. They would rather buy a new dog.

'That is the problem and it is like this everywhere. But in other countries, they have programmes for retired dogs - they find people who are willing to adopt them as pets. We cannot do this in Macau. The dog-racing centre will not allow these dogs to be given for adoption in Macau. Macau is a small place and they don't want to have any complaints about the dogs causing problems or damage. But they have no objection to them going elsewhere and that is what we are exploring.'

Choi has approached the Canidrome and the Hong Kong government to see whether greyhounds could be exported across the mouth of the Pearl River when they retire and given a new lease of life as pets, or as blood donors for pet dogs of any breed. This is common post-racing practice in countries where the sport is popular, such as the United States, Australia and Ireland.

Dr Kurt Verkest, director at Hong Kong's Pets Central veterinary chain, who has discussed the proposal with Choi, says: 'Greyhounds are used all over the world as blood-donor dogs. They have a few appealing features: they are a large dog, quiet, they tend to be sedate and they have a high percentage of red blood cells, which makes them very useful as blood donors. A normal dog has 35 to 50 per cent red bloods cells but in greyhounds, that can be 50 to 65 per cent.'

They also make surprisingly easy pets, says Verkest.

'Everybody I know who has adopted a greyhound as a pet has loved them and been delighted with them. Contrary to public opinion, they don't actually need a lot of exercise. They like to be lap dogs and sedentary because they spend most of their life in a very small kennel not being exercised. So their exercise requirements are not higher than most dogs and are lower than a lot of dogs.'

Exporting the greyhounds to Hong Kong or the mainland could save at least some of them from the fate that awaits them when their racing days end - a HK$200 lethal injection in a 'killing room' inside the Canidrome followed by a HK$1,000 disposal at a public incinerator - but there are obstacles. The main ones, as far as sending the dogs to Hong Kong is concerned, are quarantine restrictions. Because Macau is not ranked as rabies-free, any dog sent to Hong Kong would have to spend four months in quarantine, at a cost of about HK$100 a day. Choi says an exception should be made for the greyhounds, which are imported directly from Australia, are vaccinated throughout their racing lives and never set foot outside the Canidrome.

'There is absolutely no risk of the greyhounds having contact with other dogs,' he says. 'I think the Hong Kong government should grant them an exemption from the quarantine restrictions or allow them to be quarantined in veterinary clinics, where they can be used for transfusions. We want them to review the arrangement.'

So far, Choi's appeals have fallen on deaf ears.

'I spoke to the dog-racing company about this and it didn't refuse. It didn't want the dogs to be adopted in Macau but it has no objection to them going to Hong Kong or [mainland] China.'

However, there is no mechanism by which owners can sell the dogs when they are retired. The management would have to implement such a system before a dog could even leave the Canidrome.

'In Macau, we have successfully exported retired racehorses back to Australia since 2008. We send about five or six a year. Many more retired horses go to mainland China. If it's possible for retired horses, why isn't it possible for dogs?'

Calls to the Canidrome go unanswered but a spokesman for the Hong Kong Agriculture, Fisheries and Conservation Department makes its position clear: 'Hong Kong has been free from rabies for more than 20 years. Maintenance of our rabies-free status hinges upon the stringent import control of animals and relevant measures in preventing and early detection of suspected rabies case. The AFCD has no intention to lessen this requirement and put Hong Kong at risk. Rabies kills an estimated 55,000 humans annually and the AFCD will ensure the Hong Kong public is protected from this invariably fatal disease.'

Putting the dogs in quarantine in veterinary clinics is out of the question, too, the spokesman says.

'Given the frequent admission of sick animals into vet clinics, we consider they are not suitable quarantine premises for animals. Most clinics do not have facilities for the long-term keeping of dogs. The AFCD is concerned about the welfare of any dog kept for a prolonged period of time in a veterinary clinic.'

Pressure group People for the Ethical Treatment of Animals (Peta) is not pleased with what's happening in Macau and is against the sport in principle.

'The greyhound racing industry, like many of the dogs used in this cruel so-called sport, is dying,' says Peta's Rebecca Chui. 'All over the world, an increasingly informed public no longer wants to support an industry that treats greyhounds like garbage. In recent years, 27 greyhound tracks have closed in the US due to declining attendance and it is illegal in 34 states.

'Barbados, Haiti and Indonesia have all shut their once-active tracks, and former racing dogs in Guam were given to anyone who would take them after the local track closed due to dwindling profits.'

A campaign by Peta in 2009 helped block plans for a dog-racing track in the Philippines.

'Greyhounds are gentle dogs who want nothing more than to snuggle on the couch and be part of a family, ' Chui says. 'Dogs used in racing know nothing but misery, their worlds reduced to a tiny kennel and a lifetime of servitude. The cruelty begins even before a dog steps foot on a track. Countless greyhounds who breeders believe will be too slow to win races are killed each year. Dogs have been shot, bludgeoned, or simply dumped to fend for themselves.

'Dogs who are deemed good enough to race typically spend their short lives in cages and are kept muzzled at all times. They never know a kind word or a gentle touch, much less the belly rubs and companionship they deserve.'

For the time being, at least, there is no end in sight to the slaughter of the Macau greyhounds. The kill rate suggests two more greyhounds will be taken to the killing room between last night's races and the next meeting, tomorrow.

Their lives are laid bare in spreadsheets on Choi's desk. The neatly compiled statistics reveal how the bodies of young, healthy greyhounds keep leaving the Canidrome for the government incinerators. Twenty-one dogs in January. Twenty-five in February. Forty-five in March. Twenty-one in April. The figures are matched almost exactly by the import of younger greyhounds.

'Dog racing is not a sport. It is about gambling - that's all,' Choi says. 'It is terrible that there is no second chance for these dogs when they retire. They are all just put to sleep and it's very sad.

'If the industry expands, they will just breed more and more dogs. But if the racing stopped, these poor animals wouldn't be bred. They wouldn't have to come into the world just to race and then to die.'